Protection Layer Wrapping Conductive Via in BSI Image Sensors
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Solution Overview
Problem
During the fabrication of backside illumination (BSI) image sensors, the conductive material in through vias often migrates due to sidewall cuts at the interface of the carrier and active wafers, leading to conducting defects due to incomplete filling and subsequent migration of the conductive material.
Innovation Solution
A protection layer is formed on the sidewall of the through via using a mixed gas during the etching and ashing operations to prevent conductive material migration, ensuring complete filling of the via and enhancing the conducting effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive material is deposited in through vias during BSI image sensor fabrication, then electrical connections are established between carrier and active wafers, but sidewall cuts at the interface cause conductive material migration and incomplete filling
Solution Approach 1:
A protection layer is formed on the sidewalls of through vias before depositing conductive material. This preliminary action prevents sidewall cuts from causing conductive material migration during subsequent filling processes, ensuring complete and reliable electrical connections between carrier and active wafers in BSI image sensors.
2Ease of manufacture
If etching operations are performed to create through vias, then electrical pathways are formed, but sidewall cuts are created that lead to conductive material migration
Solution Approach 1:
The protection layer is deposited on the sidewalls of through vias immediately after etching but before conductive material filling. This timing prevents sidewall cuts from compromising conductive material stability, while maintaining the ease of through via formation through standard etching processes.
Solution Approach 2:
The protection layer acts as an intermediary between the etched sidewall cuts and the conductive material. It mediates the interaction by preventing direct contact between conductive material and damaged sidewalls, thereby eliminating migration while preserving the manufacturing simplicity of through via creation.
3Reliability
If conductive material is used to fill through vias, then electrical conduction is achieved, but migration occurs due to sidewall cuts causing conducting defects
Solution Approach 1:
The protection layer serves as an intermediary barrier between the conductive material and the sidewall cuts. It prevents the harmful interaction that causes conductive material migration, thereby eliminating conducting defects while maintaining reliable electrical conduction through the via.
Solution Approach 2:
The protection layer converts the harmful effect of sidewall cuts into a beneficial outcome. By providing a stable surface for conductive material deposition, it transforms the previously harmful irregular sidewalls into a controlled interface that ensures complete filling and prevents migration, turning a manufacturing challenge into a solution.
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 protection layer effectively prevents conductive material migration, ensuring reliable electrical connections and improving the conducting effect by allowing the conductive material to completely fill the through via without needing to fill sidewall cuts, thus overcoming conducting defects.
Implementation Method 1
A protection layer is formed on the sidewall of the through via using a mixed gas during the etching and ashing operations
Data Source
AI summary
A semiconductor device having a protection layer wrapping around a conductive structure is provided. The semiconductor device comprises an image sensor device layer, an interconnect layer over the image sensor device layer, a first bonding layer over the interconnect layer, a second bonding layer bonded with the first bonding layer, a substrate over the second bonding layer, and a conductive via passing through the substrate, the second bonding layer, and the first bonding layer. The conductive via comprises a protection layer and a conductive material. The protection layer is peripherally enclosed by the substrate, the second bonding layer, and the first bonding layer. The protection layer covers a sidewall cut formed at an interface of the second bonding layer and the first bonding layer. The conductive material is peripherally enclosed by the protection layer.