Scribe Line Dummy Pad Layout for Wafer Bonding Alignment
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Solution Overview
Problem
In 3D integrated circuit packaging, misalignment of metal features in bonding layers compromises wafer-to-wafer bonding, leading to weakened bonding.
Innovation Solution
A method for generating dummy pad patterns in photomask designs involving multiple alignments and overlays of dummy patterns with edge and center portions of device layouts, using stepwise photolithographic exposure to ensure symmetric dummy pad patterns in scribe line regions, facilitating vertical alignment of metal features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask design is used without dummy pad patterns, then the design process is simpler, but misalignment of metal features occurs during wafer-to-wafer bonding
Solution Approach 1:
Dummy pad patterns are pre-designed and integrated into the photomask design before the actual bonding process. These dummy patterns are positioned in scribe line regions to establish reference alignment features that guide the wafer-to-wafer bonding process, ensuring metal features align correctly without requiring complex real-time adjustment mechanisms
Solution Approach 2:
Dummy pad patterns serve as intermediary alignment references between the photomask design and the bonding process. These dummy features act as mediator elements that facilitate precise alignment by providing visible reference points during bonding, eliminating the need for direct complex alignment mechanisms between metal features
2Reliability
If dummy pad patterns are added to photomask designs, then vertical alignment of metal features is enhanced, but the photomask design and fabrication process becomes more complex
Solution Approach 1:
Dummy pad patterns are incorporated into the photomask design at the planning stage, before bonding occurs. This preliminary integration ensures that alignment references are already in place when wafers are positioned for bonding, strengthening bonding reliability by preventing misalignment rather than correcting it during the process
Solution Approach 2:
Dummy pad patterns are created as simplified copies or representations of actual pad structures, placed in non-critical scribe line regions. These copy elements replicate the alignment function of real pads without requiring the full complexity of functional pad designs, thus improving bonding reliability while adding minimal design complexity
3Manufacturing precision
If multiple alignments and overlays are performed in photomask design, then manufacturing precision of metal features is improved, but production time increases
Solution Approach 1:
Multiple alignment and overlay operations are performed during the photomask design phase rather than during wafer fabrication. By completing these precision alignment operations in the design stage using computer-aided design tools, the patent achieves high alignment precision without adding time to the actual manufacturing process
Solution Approach 2:
Manual or mechanical alignment operations are replaced with automated computer-aided design and layout software that performs multiple alignments and overlays computationally. This substitution of mechanical processes with digital computation achieves high precision alignment rapidly, improving manufacturing precision without increasing production time
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
Enhances vertical alignment of metal features, thereby strengthening wafer-to-wafer bonding and reducing process instability.
Implementation Method 1
using stepwise photolithographic exposure to ensure symmetric dummy pad patterns in scribe line regions
Data Source
AI summary
The present disclosure provides method to generate a dummy pad pattern. A method according to embodiment of the present disclosure includes receiving a design layout that includes a device region disposed in a scribe line region, identifying a center portion of the scribe line region surrounding the device region and an edge portion surrounding the center portion, dividing the edge portion into a plurality of rectangular areas, super-positioning a dummy pattern on each of the plurality of rectangular areas to obtain edge dummy patterns, super-positioning the dummy pattern on the center portion to obtain center dummy patterns, carving out a portion of the dummy pattern corresponding to the device region from the center dummy patterns to obtain net center dummy patterns, generating a scribe line dummy pattern based on the edge dummy patterns and the net center dummy patterns, and fabricating a first photomask including the scribe line dummy pattern.