LCoS Mirror Contact Fill CMP for DBR Thickness Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Advanced liquid crystal on silicon (LCoS) devices face challenges in achieving uniformity and optical performance due to variations in the thickness of the first layer of the distributed Bragg reflector (DBR), which are introduced by non-uniformities in the surface resulting from the deposition of insulating oxide materials during fabrication.
Innovation Solution
A method involving etching a contact hole through the mirror layer, filling it with a fill material, and using chemical mechanical polishing (CMP) to remove excess fill material selectively, ensuring the interface between the mirror layer and the DBR is substantially free of fill material, thereby maintaining uniform thickness and improving optical stack uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fill material is deposited to fill contact holes through the mirror layer, then electrical isolation of contacts from the mirror layer is achieved, but non-uniformities in the surface are introduced that cause variation in the thickness of the first layer of the DBR
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical polishing (CMP) to remove excess fill material before depositing the first layer of the distributed Bragg reflector (DBR). This preliminary removal of non-uniformities ensures that the subsequent DBR layer can be deposited on a uniform surface, achieving both electrical isolation through the fill material and thickness uniformity for optimal optical performance
Solution Approach 2:
The patent applies the taking out principle by selectively removing the excess fill material that creates surface non-uniformities. Through CMP processing, the harmful portions of the fill material are extracted from the surface, leaving only the necessary fill material within the contact holes for electrical isolation, while restoring surface uniformity for the DBR deposition
2Ease of manufacture
If variation in thickness of the first layer of the DBR is accommodated, then the non-uniform surface can be covered, but the optical performance of the DBR is significantly impaired
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical polishing (CMP) to remove excess fill material before depositing the first layer of the distributed Bragg reflector (DBR). This preliminary removal of non-uniformities ensures that the subsequent DBR layer can be deposited on a uniform surface, achieving both electrical isolation through the fill material and thickness uniformity for optimal optical performance
Solution Approach 2:
The patent applies parameter changes by controlling the CMP process parameters (down force, rotation rate, slurry flow rate) to achieve the optimal balance between removing excess fill material and maintaining surface uniformity. By adjusting these parameters, the process transforms the surface topology from non-uniform to uniform, enabling high-quality DBR deposition with minimal thickness variation
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 results in improved optical performance by limiting wavelength variation and enhancing reflectivity, making LCoS structures more suitable for display devices by maintaining the thickness of the first layer of the DBR and reducing blue or red shifting of the reflectivity spectrum.
Implementation Method 1
removing a portion of the fill material external to the contact hole by chemical mechanical polishing landing on the mirror layer
Data Source
AI summary
Processing methods may be performed to form a filled contact hole in a mirror layer of a semiconductor substrate. The method may include forming a contact hole through a mirror layer of the semiconductor substrate by an etch process. The method may include filling the contact hole with a fill material. A portion of the fill material may overlie the mirror layer. The method may also include removing a portion of the fill material external to the contact hole by chemical mechanical polishing landing on the mirror layer.