Lithography Process for Multi-Layer Thin Film Encapsulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for depositing and protecting dielectric-metal coatings are not compatible with wafers that have bond pads or uncoated areas, requiring dual layer patterning or special deposition angles, and struggle with optimizing the lift-off profile for effective encapsulation and spectral performance.
Innovation Solution
A single lithography process involving multiple developing, baking, and lifting steps that utilize the reflow characteristics of photoresist to coat multiple thin films without re-patterning, allowing for encapsulation and profile optimization of multi-spectral patterned thin film coatings through a double develop and dry lift-off process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous blanket coating is used over coated and uncoated patterned regions, then the metal layer edges are passivated and protected from oxidation and corrosion, but the method is not compatible with wafers that have bond pads or similar uncoated area requirements
Solution Approach 1:
The coating process is segmented into multiple deposition steps with intermediate lithography and development steps. The first dielectric layer is deposited and patterned, then a second dielectric layer is deposited and patterned separately. This segmentation allows different regions of the wafer to have different coating configurations, enabling compatibility with bond pads and uncoated areas while still providing edge protection where needed.
Solution Approach 2:
The first dielectric layer is deposited and patterned in advance before the second dielectric layer deposition. This preliminary action creates an encapsulating structure that protects the metal layer edges. The intermediate development step removes portions of the first dielectric layer to create the necessary profile for the second layer, allowing subsequent uncoated areas to be formed while maintaining edge protection in other regions.
2Adaptability or versatility
If dual layer patterning or special deposition angles are used to accommodate wafers with bond pads or uncoated areas, then compatibility with such wafers is achieved, but the process complexity increases
Solution Approach 1:
The lithography process is made dynamic through multiple development steps. After depositing the first dielectric layer, a development step creates an undercut profile. Then the second dielectric layer is deposited, followed by another development step that removes additional material. This dynamic, multi-step approach allows the same basic process to adapt to different wafer configurations (with or without bond pads) without requiring fundamentally different methodologies or special deposition angles.
3Reliability
If the photoresist profile is sloped to permit effective encapsulation of the first deposited film by the second deposited film, then encapsulation is achieved, but the lift-off profile is compromised
Solution Approach 1:
The development process is applied periodically at multiple stages: first after depositing the initial resist pattern, then after depositing the second dielectric layer. These periodic development actions create and maintain the undercut profile at critical stages, ensuring both effective encapsulation during deposition and proper lift-off characteristics afterward. The periodic intervention of development steps reconciles the conflicting requirements of encapsulation and lift-off profile.
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
Enables the encapsulation of metal layers with minimized transition zones, improving spectral performance and ease of lift-off, while maintaining the undercut profile, thus overcoming the limitations of prior art methods.
Implementation Method 1
subsequent thermal processing can lessen or eliminate this undercut. On heating, the top layer of photoresist reflows and pulls back from the edge leading to a reduced lift-off profile
Implementation Method 2
The invention of this disclosure is a single lithography process for multi-layer metal/dielectric coatings
Data Source
AI summary
A single lithography process for multi-layer metal/dielectric coatings using a series of developing, baking, and lifting steps to coat two or more thin films without re-patterning that results in the encapsulation and profile optimization of multi-spectral patterned thin film coatings is disclosed.