Self-Planarizing ONO Passivation for LCoS Pixel Electrodes
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Solution Overview
Problem
Conventional methods for achieving a substantially planar passivation layer over pixel electrodes in Liquid Crystal on Silicon (LCoS) devices require complicated planarization and etch back steps, which are inefficient and difficult to perform.
Innovation Solution
A self-planarizing passivation dielectric is formed using an Oxide-Nitride-Oxide (ONO) stack with a thickness equal to twice the gap width between pixel electrodes, deposited over pixel electrodes and in the gaps, eliminating the need for complex planarization and etch back processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional planarization and etch back steps are used to achieve a substantially planar passivation layer, then the planarity of the passivation surface is improved, but the manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent applies the self-service principle by designing a passivation layer formation process that automatically achieves planarity through the inherent properties of the deposited dielectric material. The dielectric is deposited to a thickness that naturally fills the gaps between pixel electrodes and creates a planar top surface without requiring external planarization or etch back interventions. The system essentially plans and executes its own planarization through controlled deposition parameters.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the deposition thickness of the dielectric material in the passivation layer. By setting the deposition thickness to a specific value (equal to the gap width between pixel electrodes), the process transforms the non-planar surface into a planar one through material addition rather than removal. This parameter-based approach replaces complex mechanical or chemical planarization processes.
2Manufacturing precision
If conventional planarization and etch back steps are used to achieve a substantially planar passivation layer, then the planarity of the passivation surface is improved, but the manufacturing time and process steps increase
Solution Approach 1:
The passivation layer formation process performs self-planarization by depositing dielectric material to a thickness that inherently creates a planar top surface. This eliminates the need for separate planarization and etch back process steps, reducing the total manufacturing cycle time and increasing production efficiency while maintaining the required planarity.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and pre-setting the dielectric deposition thickness during the process design phase. This preliminary determination of the optimal thickness value ensures that the passivation layer achieves planarity in a single deposition step, preventing the need for subsequent corrective planarization operations and reducing overall manufacturing time.
3Manufacturing precision
If a thick dielectric layer is deposited to fill gaps between pixel electrodes, then the planarity of the passivation surface is improved, but the amount of material and process complexity increase
Solution Approach 1:
The patent optimizes material consumption by precisely controlling the dielectric deposition thickness parameter. The thickness is set to exactly match the gap width between pixel electrodes, ensuring that material is deposited only where needed to achieve planarity. This precise parameter control minimizes excess material deposition while still achieving the required planar surface.
Solution Approach 2:
The passivation layer structure applies local quality by having the dielectric material specifically target and fill the gap regions between pixel electrodes. The deposition process is localized to where it is most needed (in the gaps) rather than uniformly thickening the entire substrate, thereby reducing overall material consumption while achieving planarity in the critical regions.
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 approach provides a substantially planar passivation surface over pixel electrodes without the need for complicated planarization and etch back steps, enhancing reflectivity and integration with liquid crystal layers while reducing manufacturing complexity.
Implementation Method 1
A self-planarizing passivation dielectric can be formed by depositing an Oxide-Nitride-Oxide (ONO) stack, for example, by utilizing a plasma enhanced chemical vapor deposition (PECVD) process
Implementation Method 2
A self-planarizing passivation dielectric can be formed by depositing an Oxide-Nitride-Oxide (ONO) stack, for example, by utilizing a plasma enhanced chemical vapor deposition (PECVD) process
Implementation Method 3
A self-planarizing passivation dielectric can be formed by depositing an Oxide-Nitride-Oxide (ONO) stack, for example, by utilizing a plasma enhanced chemical vapor deposition (PECVD) process
Data Source
AI summary
According to an exemplary embodiment, a liquid crystal on silicon (LCoS) structure includes a number of pixel electrodes overlying an interlayer dielectric, where diagonally adjacent pixel electrodes are separated by a gap. The LCoS structure further includes a self-planarizing passivation dielectric situated over the pixel electrodes and in the gap, where the self-planarizing passivation dielectric has a selected thickness. The self-planarizing passivation dielectric can be an Oxide-Nitride-Oxide (ONO) stack. The selected thickness of the self-planarizing passivation dielectric causes the self-planarizing passivation dielectric to have a substantially planar top surface. In one embodiment, the thickness of the self-planarizing passivation dielectric can be approximately equal to twice a width of the gap.