Three-Layer Image Sensor Interconnects Without Deep Pad Holes
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Solution Overview
Problem
The manufacturing process of stacked solid-state imaging devices faces challenges such as deep pad holes, which complicate the formation of connections and lead to issues like residual resist and deposited substances causing defects, and the difficulty in blocking light from hot carriers, resulting in increased costs and reduced performance.
Innovation Solution
The solution involves a three-layer stacked structure where the aluminum pad is placed in the first semiconductor substrate, allowing for shallower pad holes and effective blocking of light from hot carriers without the need for deep connections, using a combination of copper wires and aluminum pads to manage electrical connections and noise prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection holes are formed deep through substrates to electrically connect stacked semiconductor substrates, then electrical connectivity between layers is achieved, but manufacturing complexity and costs increase significantly
Solution Approach 1:
The invention transitions from vertical through-substrate connections to a combination of partial-depth holes in the first substrate and surface-level pads on the second substrate. This dimensional change eliminates the need for deep through-holes while achieving the same electrical connectivity function through a different spatial arrangement.
Solution Approach 2:
The connection path is segmented into two parts: connection holes formed only in the first substrate to a certain depth, and separate pads formed on the surface of the second substrate. This segmentation avoids the complexity of forming single deep through-holes spanning multiple substrates while maintaining electrical connectivity.
2Manufacturing precision
If small contact holes of about 1 micrometer are formed, then substrate must be thinned to the utmost limit, but complex steps such as attaching to support substrate are required
Solution Approach 1:
Instead of thinning the substrate to the utmost limit, the invention uses partial-depth connection holes that extend only to the necessary depth to reach the pads on the second substrate. This partial action achieves the required precision without the excessive substrate thinning that would necessitate support substrate attachment.
3Manufacturing precision
If connection holes with high aspect ratio are formed, then specific CVD materials like tungsten must be used, but material selection becomes limited
Solution Approach 1:
The invention changes the depth parameter of connection holes, forming them only in the first substrate rather than as deep through-holes. This parameter change reduces the aspect ratio, thereby expanding material options to include aluminum and copper in addition to tungsten, as lower aspect ratios do not require the specialized coatability of CVD materials.
4Reliability
If deep pad holes are formed in stacked structure, then residual resist and deposited substances cause defects, but manufacturing quality decreases
Solution Approach 1:
The invention extracts the pads from deep within the stacked structure and places them on the surface of the second substrate. This extraction eliminates the deep pad holes that trap residual resist and deposited substances, thereby preventing manufacturing defects while maintaining electrical connection reliability.
Data Source
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AI summary
A semiconductor device including a first semiconductor section including a first wiring layer at one side thereof, the first semiconductor section further including a photodiode, a second semiconductor section including a second wiring layer at one side thereof, the first and second semiconductor sections being secured together, a third semiconductor section including a third wiring layer at one side thereof, the second and the third semiconductor sections being secured together such the first semiconductor section, second semiconductor section, and the third semiconductor section are stacked together, and a first conductive material electrically connecting at least two of (i) the first wiring layer, (ii) the second wiring layer, and (iii) the third wiring layer such that the electrically connected wiring layers are in electrical communication.