Micro Bump Planarization via Pattern Density Adjustment
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Solution Overview
Problem
In semiconductor wafer packaging, achieving planarization of metal bumps or balls is challenging due to uneven heights, which can lead to cold joints and poor connectivity between the IC dies and the carrier substrate.
Innovation Solution
The technique involves adjusting the pattern density of micro bump structures on the wafer surface by modifying the surface area of existing bumps or adding dummy bumps, using a combination of local and global convolution operations and Gaussian filtering to ensure consistent heights across the wafer, thereby maintaining planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal bumps are deposited on metal pads without pattern density adjustment, then the manufacturing process is simple, but the bump heights become uneven causing cold joints
Solution Approach 1:
The patent applies preliminary action by adjusting the pattern density of metal pads before bump deposition. The method calculates a target pattern density and modifies the pad layout in advance to compensate for expected height variations, ensuring uniform bump heights after deposition without requiring complex post-processing planarization steps
Solution Approach 2:
The patent changes the pattern density parameter of the metal pad array to control bump height uniformity. By adjusting the spacing and distribution of pads (pattern density), the method directly influences the resulting bump heights, transforming a geometric parameter into a control variable for height uniformity
2Manufacturing precision
If planarization is attempted on metal bump side, then surface flatness may be improved, but the process is difficult to arrange or maintain
Solution Approach 1:
Instead of performing planarization after bump formation, the patent performs preliminary action by adjusting the pad pattern density before bump deposition. This preventive approach eliminates the need for difficult post-deposition planarization processes while achieving the same surface flatness outcome
Solution Approach 2:
The patent extracts the planarization function from the post-deposition process and relocates it to the pre-deposition pad design stage. By taking out the height control function from the manufacturing process and embedding it in the pattern density calculation, the method eliminates complex planarization steps
3Reliability
If uneven heights on metal bumps occur, then the mounting process is simpler, but cold joints occur causing poor connectivity
Solution Approach 1:
The patent uses parameter changes in pattern density to directly control bump height consistency. By calculating and adjusting the pattern density parameter during design, the method ensures that all bumps achieve uniform heights, preventing cold joints and ensuring reliable connectivity
Solution Approach 2:
The patent implements feedback by using the measured or simulated bump heights as input to recalculate the optimal pattern density. This iterative feedback loop allows the method to compensate for process variations and achieve consistent bump heights across the substrate
Data Source
AI summary
The current disclosure describes techniques for managing planarization of features formed on a semiconductor wafer. The disclosed techniques achieve relative planarization of micro bump structures formed on a wafer surface by adjusting the pattern density of the micro bumps formed within various regions on the wafer surface. The surface area size of a micro bump formed within a given wafer surface region may be enlarged or reduced to change the pattern density. A dummy micro bump may be inserted into a given wafer surface region to increase the pattern density.