Copper Bumping Process Peripheral Wall Protection
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Solution Overview
Problem
Conventional bumping processes face issues with copper ionization and indentation of peripheral walls, leading to short circuits due to exposure of dented first and second peripheral walls during the etching process.
Innovation Solution
A bumping process involving a substrate with bond pads, a copper metal layer, photoresist patterning, and copper bumps with a nickel and coupling layer connection, followed by a protective layer and dielectric layer to prevent ionization by covering the exposed peripheral walls, and reducing the thickness of the protective layer while enhancing structural strength and reducing sealing resin usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the etching process is used to remove the metal layer with copper, then the under bump metallurgy layer is formed, but the copper bumps are etched as well leading to indentation of the peripheral walls
Solution Approach 1:
A protective layer is introduced as an intermediary between the etching process and the copper bumps. This protective layer selectively protects the copper bumps from etching while allowing the metal layer to be removed, thereby preventing peripheral wall indentation and maintaining manufacturing precision without compromising the ease of manufacture.
2Reliability
If the protective layer is made thicker to prevent ionization, then the structural strength is improved, but the thickness of the protective layer increases
Solution Approach 1:
The protective layer is applied selectively only in critical areas where ionization prevention is needed, such as around the copper bumps and peripheral walls, rather than uniformly across the entire structure. This localized application prevents ionization while minimizing the overall thickness increase and maintaining structural strength.
3Strength
If the protective layer thickness is reduced, then the package structural strength is improved, but the ionization phenomenon occurs more easily
Solution Approach 1:
The protective layer serves as a mediator that allows for thinner overall protective structures while still preventing ionization in critical areas. By strategically positioning the protective layer where ionization is most likely to occur, the design achieves both reduced thickness for improved structural strength and effective ionization prevention.
Data Source
AI summary
A bumping process comprises steps of forming a metal layer with copper on a substrate, and the metal layer with copper comprises a plurality of first zones and second zones; forming a photoresist layer on the metal layer with copper; patterning the photoresist layer to form a plurality of openings; forming a plurality of copper bumps within the openings, each of the copper bumps covers the first zones and comprises a first top surface; forming a connection layer on the first top surface; removing the photoresist layer; removing the second zones and enabling each of the first zones to form an under bump metallurgy layer, wherein the under bump metallurgy layer, the copper bump, and the connection layer possess their corresponded peripheral walls, and covering sections of a first protective layer formed on the connection layer may cover those peripheral walls to prevent ionization phenomenon.