Fan-Out Semiconductor Package Cu Post Structure for High-Aspect-Ratio Openings
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Solution Overview
Problem
In manufacturing fan out semiconductor packages, large aspect ratios of openings lead to residues and undercuts during the formation of Cu posts, complicating subsequent processes.
Innovation Solution
The semiconductor package design includes vertical conductive structures with a stacked configuration of conductive pillar portions, using a combination of positive and negative type photoresist layers to form openings with varying aspect ratios, which are then filled with conductive material to create Cu posts without residue issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single photoresist layer is used to form openings with large aspect ratio, then the Cu post formation becomes difficult, but using multiple photoresist layers increases process complexity
Solution Approach 1:
The photoresist structure is divided into multiple segments: a first photoresist layer and a second photoresist layer with different types (positive and negative). Each layer forms a portion of the opening, allowing the total aspect ratio to be distributed across multiple segments rather than requiring a single high aspect ratio opening.
Solution Approach 2:
Different regions of the photoresist structure have different properties. The first photoresist layer has different characteristics than the second photoresist layer, with each layer optimized for its specific function in forming the overall opening structure.
2Manufacturing precision
If openings with large aspect ratio are formed, then Cu post formation is challenging, but reducing opening depth limits the achievable aspect ratio
Solution Approach 1:
The total opening depth is segmented into two portions: a first opening formed in the first photoresist layer and a second opening formed in the second photoresist layer. This segmentation allows the cumulative depth to achieve a large aspect ratio while each individual layer remains manufacturable.
Solution Approach 2:
The first photoresist layer is formed and processed first to create the initial opening structure. Then the second photoresist layer is formed to extend the opening further. This preliminary action sequence allows progressive deepening of the opening without requiring the entire depth to be formed in a single step.
3Reliability
If conventional photoresist processes are used, then residues and undercuts occur, but alternative methods increase manufacturing complexity
Solution Approach 1:
The patent uses a composite photoresist structure combining two different photoresist materials with complementary properties. This composite approach leverages the strengths of each material type to achieve clean opening formation without the defects typically associated with single-material photoresist processes.
Solution Approach 2:
The patent changes key parameters of the photoresist system by using different photoresist types (positive and negative) with different chemical and physical properties. This parameter change enables the formation of high aspect ratio openings without residues or undercuts that plague conventional single-type photoresist processes.
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 allows for the formation of Cu posts with large aspect ratios without generating residues under the photoresist layer, enhancing the manufacturing efficiency and reliability of the semiconductor package.
Implementation Method 1
a first photoresist layer and a second photoresist layer are exposed to light
Implementation Method 2
a first photoresist layer and a second photoresist layer are sequentially formed on a lower redistribution layer, third openings are formed to penetrate the second photoresist layer to expose portions of a light blocking layer, the portions of the light blocking layer exposed by the third openings are etched to form second openings that expose the first photoresist layer, first openings are formed to penetrate the first photoresist layer
Data Source
AI summary
Semiconductor package includes lower redistribution layer providing first redistribution wirings and having first region and second region surrounding the first region, semiconductor chip disposed on the first region and electrically connected to the first redistribution wirings, sealing member covering the semiconductor chip on the lower redistribution layer, plurality of vertical conductive structures penetrating the sealing member on the second region and electrically connected to the first redistribution wirings, upper redistribution layer disposed on the sealing member and having second redistribution wirings electrically connected to the plurality of vertical conductive structures and plurality of bonding pads. The vertical conductive structures are bonded to the bonding pad and extend vertically from the plurality of bonding pads. The vertical conductive structure includes first to third conductive pillar portions sequentially stacked. The first conductive pillar portion has first length and the third conductive pillar portion has third length greater than the first length.