Wafer Trim Edge Oxide Encapsulation for Stable Copper Bonding
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Solution Overview
Problem
Conventional wafer trimming processes without edge protection lead to unstable trim edges, resulting in chipping and bond integrity issues, which cause significant line yield loss and scrap in semiconductor fabrication.
Innovation Solution
Implementing a conformal silicon oxide deposition on the wafer post-trim to protect the trim edge, followed by a short polish to ensure a smooth surface for bonding, and encapsulating copper burrs with silicon oxide to prevent interference with bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wafer trimming processes are used without edge protection, then the trimming operation can be completed, but the trim edges become unstable resulting in chipping and bond integrity issues
Solution Approach 1:
A conformal silicon oxide layer is deposited on the wafer surface before the trim operation to protect the edge during cutting. This preliminary protective action prevents chipping and maintains edge stability throughout the trimming process, directly resolving the contradiction between achieving clean trim edges and maintaining bond integrity.
Solution Approach 2:
The silicon oxide layer acts as a cushioning protective barrier deposited beforehand on the wafer surface. This layer absorbs and distributes stresses during trimming, preventing direct mechanical damage to the silicon edge, thereby maintaining both trim edge stability and preventing chipping that would compromise bond integrity.
2Reliability
If trim edge protection is implemented with conformal silicon oxide deposition, then bond integrity is improved, but additional process steps are required
Solution Approach 1:
The conformal silicon oxide deposition serves multiple functions simultaneously: it protects the trim edge during cutting, provides a smooth surface for subsequent bonding operations, and acts as a stress buffer. By combining these functions into a single process step, the patent improves bond integrity while minimizing the increase in process complexity.
3Productivity
If copper features are made larger and denser to increase capacity, then functional density is improved, but trim edge stability deteriorates due to copper burrs interfering with bonding
Solution Approach 1:
The conformal silicon oxide layer acts as an intermediary barrier between the copper features and the bonding interface. It encapsulates copper burrs and prevents them from interfering with the bonding process, allowing larger and denser copper features to be used without compromising bonding quality, thereby enabling increased functional density.
Solution Approach 2:
The thin conformal silicon oxide film flexibly conforms to the complex three-dimensional topology of dense copper features while providing continuous protection. This thin film encapsulates copper burrs and irregularities, maintaining bonding quality even with high-density copper interconnect structures.
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
Significantly reduces line yield loss and expands the process window for thicker bow compensation nitride, making the process more robust to larger and denser copper features, while ensuring bond integrity.
Implementation Method 1
conformal silicon oxide deposition on the wafer post-trim
Implementation Method 2
followed by a short polish to ensure a smooth surface for bonding
Data Source
Figure 1A~1B
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
Wafer trim edge protection is described. In an example, an integrated circuit structure includes a substrate having a feature including copper therein or thereon, the substrate having a recessed sidewall. A first layer including silicon and oxygen above the feature including copper. A burr including copper extending from the feature including copper and along the recessed sidewall of the substrate, along a side of the first layer including silicon and oxygen, and on a top of the first layer including silicon and oxygen. A layer including silicon and nitrogen is below or above the first layer including silicon and oxygen. A second layer including silicon and oxygen above the layer including silicon and nitrogen, wherein the second layer including silicon and oxygen encapsulates the burr including copper.