3D Memory Dummy Conductive Layer for Laser Shielding
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Solution Overview
Problem
In semiconductor storage devices like 3D nonvolatile memory, laser irradiation for forming active layers can damage lower wiring layers due to penetration of laser light, particularly affecting copper wiring with low melting points.
Innovation Solution
Incorporating dummy layers with higher melting points, such as tungsten, at specific positions overlapping with copper wiring in the stacking direction to shield the laser light and prevent damage, while also expanding the irradiation intensity range for activation annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light is irradiated from above to form active layers at upper ends of pillars, then the active layer formation is achieved, but the laser light penetrates into the semiconductor storage device causing damage to lower wiring layers
Solution Approach 1:
A dummy layer is introduced as an intermediary component between the stacked body and the lower copper wiring layer. This dummy layer serves as a mediator that absorbs or blocks the penetrating laser light, preventing it from reaching and damaging the copper wiring layer while allowing the active layer formation process to proceed normally above.
Solution Approach 2:
The dummy layer is positioned in advance below the stacked body at a location where laser light penetration is anticipated to occur. This pre-positioned protective layer provides beforehand cushioning against the harmful laser light, ensuring that the copper wiring layer is protected before the laser irradiation damage can occur during active layer formation.
2Object-affected harmful factors
If dummy layers are added to shield laser light, then protection against laser penetration is achieved, but device complexity increases
Solution Approach 1:
The dummy layer is designed to serve multiple functions simultaneously: it acts as a protective shield against laser light penetration, provides structural support in the region below the stacked body, and can serve as an additional conductive path or electrical isolation layer. This multi-functionality reduces the need for separate protective components, thereby minimizing the increase in device complexity.
Solution Approach 2:
The dummy layer is selectively positioned only in specific regions where laser light penetration is a concern, rather than uniformly across the entire device. This localized approach provides protection precisely where needed while avoiding unnecessary complexity in regions where the protective function is not required, thus optimizing the balance between protection and device simplicity.
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
Prevents damage to copper wiring layers during laser irradiation and enhances the effectiveness of activation annealing by providing a sufficient shielding effect, ensuring the integrity and functionality of the semiconductor storage device.
Implementation Method 1
A part of the laser light may penetrate into the semiconductor storage device, causing damage such as melting the lower wiring layer
Implementation Method 2
Incorporating dummy layers with higher melting points, such as tungsten, at specific positions overlapping with copper wiring in the stacking direction to shield the laser light and prevent damage
Data Source
AI summary
A semiconductor storage device includes transistors disposed on a substrate; a first metal wiring layer disposed over the transistors at a first position, the first metal wiring layer including a first metal wiring; a stacked body, disposed above the first metal wiring layer, including a first conductive layers and first insulating layers alternately stacked; a pillar including a semiconductor layer that includes a first type impurity in an upper end and penetrates through the stacked body; and a second conductive layer disposed at a second position further from the substrate than the first position, overlapped with the first metal wiring or another metal wiring in the first metal wiring layer, and not electrically connected to any of the transistors, the first conductive layers, or the first metal wiring layer. The second conductive layer has a higher melting point than the first metal wiring.