Semiconductor Electrode Pad Material Selection for Bump Formation Control
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Solution Overview
Problem
Conventional semiconductor devices face issues with 'left bumps' during dicing, leading to electrical leakage and a reduction in the number of semiconductor chips obtainable from a wafer due to the need for a wider scribe grid to prevent bump remnants, which increases the area required for the scribe grid and decreases chip production.
Innovation Solution
The semiconductor device features multilayered electrode pads where the uppermost pad on the scribe grid is made of a metal with lower ionization tendency (Cu) to prevent bump formation, while the uppermost pad on the semiconductor chip, made of a higher ionization tendency metal (Al), forms bumps and plating coats, ensuring no bumps are left during dicing and allowing for selective electroless plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wider scribe grid is used to prevent bump remnants during dicing, then electrical leakage from left bumps is prevented, but the area available for semiconductor chips decreases
Solution Approach 1:
The patent applies local quality by making the uppermost electrode pad material specific to the scribe grid (different from chip electrode pads) to selectively prevent bump formation only where needed. This localized material differentiation allows bump prevention at scribe grid locations without affecting chip areas, thereby maintaining narrow scribe grid width while preventing electrical leakage from left bumps.
2Ease of manufacture
If electroless plating is performed on all electrode pads, then uniform bump formation occurs, but bumps are formed on scribe grid pads causing left bumps during dicing
Solution Approach 1:
The patent implements local quality by specifying that the uppermost electrode pad of the scribe grid is made of a specific metal material that prevents bump formation, while chip electrode pads use materials that do form bumps. This localized material differentiation enables selective bump formation - bumps form on chip pads as needed but are prevented on scribe grid pads, eliminating left bumps during dicing.
Solution Approach 2:
The patent applies parameter changes by controlling the metal material composition of electrode pads based on their location (scribe grid vs. chip). By changing the material parameter of the uppermost electrode pad in the scribe grid region, the patent selectively controls bump formation behavior - preventing bumps where they would cause harm during dicing while allowing them where they are needed for electrical connection.
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
This approach prevents electrical leakage from 'left bumps' and maintains a narrower scribe grid, thereby increasing the number of semiconductor chips that can be produced from a single wafer while enabling selective electroless plating.
Implementation Method 1
Al which is a material for the electrode pad 5 (6) is dissolved in an electroless Zn plating solution as Al ions 6a with difference in ionization tendency between Al and Zn (ionization tendency: Al>Zn). Then, Zn ions 7a in the electroless Zn plating solution are deposited on the electrode pad 5 (6); thus, the Zn plating layer 7 is formed.
Implementation Method 2
Al which is a material for the electrode pad 5 (6) is dissolved in an electroless Zn plating solution as Al ions 6a with difference in ionization tendency between Al and Zn
Data Source
AI summary
An uppermost one of multilayered electrode pads, on which a bump and a plating coat will be formed, is made of metal having high ionization tendency, particularly, Al. On the other hand, an uppermost one of multilayered electrode pads, on which none of the bump and the plating coat will be formed, is made of metal having low ionization tendency, particularly, Cu.