Cylindrical Electrode Geometry for Fine-Pitch Semiconductor Bonding
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Solution Overview
Problem
Conventional flip-chip bonding faces challenges in forming uniform bumps and achieving reliable bonding at electrode pitches of 20 μm or less, where the bump size becomes finer and bonding becomes difficult.
Innovation Solution
The use of cylindrical electrodes with an inwardly inclined shape, formed integrally with the second electrode, allows for mechanical and electrical connection with reduced pressure and improved reproducibility, simplifying the manufacturing process and preventing peeling issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bump electrodes are used for flip-chip bonding, then bonding can be performed at larger pitches (50 μm or more), but bonding becomes difficult and uniform bump formation becomes impossible at smaller pitches (20 μm or less)
Solution Approach 1:
The patent applies the spheroidality principle by replacing conventional dome-shaped bumps with cylindrical electrodes. The cylindrical shape provides a flat top surface that facilitates reliable bonding at small pitches (20 μm or less), while the curved side walls maintain mechanical strength. This geometric transformation resolves the contradiction by enabling uniform electrode formation and reliable bonding even at fine pitch dimensions where conventional bumps fail.
2Measurement precision
If the pitch is reduced to 20 μm or less, then higher resolution detection is achieved, but the bump size becomes finer making uniform formation and bonding difficult
Solution Approach 1:
The cylindrical electrode geometry with its flat top surface and vertical side walls enables precise formation at small pitches. The curvature transition from conventional dome shapes to cylindrical forms allows better control during fabrication processes, maintaining uniformity even when pitch is reduced to 20 μm or less for high-resolution detection applications.
Solution Approach 2:
The patent changes the geometric parameters of the electrode from dome-shaped to cylindrical, fundamentally altering the formation process characteristics. This parameter change enables the electrodes to be formed uniformly at smaller dimensions, directly supporting high-resolution detection while maintaining manufacturing precision at fine pitch scales.
3Measurement precision
If smaller bonding area is used to achieve smaller pitch, then higher resolution is achieved, but the pressure required for bonding increases
Solution Approach 1:
The cylindrical electrode shape with its flat top surface distributes bonding pressure more effectively compared to dome-shaped bumps. This geometric configuration allows smaller bonding areas to achieve high resolution while maintaining acceptable bonding pressure levels, as the flat contact area provides better stress distribution during the bonding process.
Data Source
AI summary
In a method for manufacturing a radiation detector, counter pixel electrodes 33 are formed on a counter substrate 2 at positions facing a plurality of pixel electrodes formed on a signal reading substrate, and wall bump electrodes 34 are further formed on the counter pixel electrodes 33. In order to achieve the above, a resist R is applied, and the resist R is exposed to light to form openings O. When Au sputter deposition is performed on the openings O, only some of the Au is deposited on the bottom surface in the openings O as the counter pixel electrodes 33. The rest of the Au is not deposited on the bottom surface in the openings O, and the most of the remaining Au adheres to the inner walls of the openings O to form wall bump electrodes 34. The bump electrodes 34 are cylindrical, making it possible to reduce the pressure acting on the signal reading substrate by an extent corresponding to the decrease in the bonding area in comparison to conventional bump-shaped bump electrodes. The decrease in the bonding area also makes it possible to correspondingly improve the reproducibility of forming the diameter of the electrodes, and make reliable connection possible.