Semiconductor Conductor Formation via Oxidation Masking
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Solution Overview
Problem
Conventional wafer level package (WLP) manufacturing faces challenges such as the undercut problem, high photoresist consumption, and decreased yield due to the need for thick and expensive photoresist masks, leading to increased manufacturing costs.
Innovation Solution
A method involving the formation of first and second seed metal layers on a semiconductor chip, where the exposed portions of the first seed metal layer are oxidized and then plated, allowing for the removal of the metal oxide without undercutting, using a sulfuric acid liquid and acid electrolyte, and employing a thinner second seed metal layer to minimize photoresist usage and reduce edge bead removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thick photoresist mask is used to prevent undercut, then manufacturing precision is improved, but manufacturing cost increases and photoresist consumption increases
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a buffered oxide etch (BOE) solution with controlled pH and composition, allowing thin photoresist to achieve the same protective effect that previously required thick photoresist with conventional etchants
Solution Approach 2:
The patent employs inexpensive, easily removable photoresist that can be applied in thin layers, replacing the need for expensive thick photoresist masks. The photoresist serves its protective function temporarily during etching and is then completely removed without residue
2Manufacturing precision
If thick photoresist mask is used to prevent undercut, then manufacturing precision is improved, but photoresist consumption increases
Solution Approach 1:
By modifying the etching chemistry to use buffered oxide etch with controlled parameters, the patent enables effective undercut prevention with minimal photoresist thickness, directly reducing photoresist material consumption
Solution Approach 2:
The patent applies photoresist only to the extent necessary for pattern definition and protection during etching, using just enough material to achieve the protective function without excess application that would increase consumption
3Ease of operation
If photoresist is removed to width of 400 micrometers for edge bead removal, then ease of operation is improved, but yield decreases
Solution Approach 1:
The patent applies different photoresist removal strategies to different locations on the wafer: minimal removal at chip locations (preserving yield) versus targeted removal only where electrode contact is actually needed, rather than uniform wide removal that sacrifices edge chips
Solution Approach 2:
The patent segments the photoresist removal process into location-specific operations, treating center wafer chips and edge wafer chips differently based on their specific contact requirements, thereby preserving yield while maintaining operational ease
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 effectively reduces the undercut issue, improves semiconductor package yield, and decreases manufacturing costs by using less expensive photoresist, thereby enhancing the efficiency of conductor formation in semiconductor devices.
Implementation Method 1
oxidizing the exposed portions of the first seed metal layer to form a metal oxide
Implementation Method 2
removing the metal oxide... using a sulfuric acid liquid
Implementation Method 3
plating a metal on a surface of the first seed metal layer exposed by removing the at least one mask
Data Source
AI summary
Provided is a method of forming conductors (e.g., metal lines and/or bumps) for semiconductor devices and conductors formed from the same. First and second seed metal layers may be formed. At least one mask may be formed on a portion on which a conductor is to be formed. An exposed portion may be oxidized. The oxidized portion may be removed. A conductive structure may be formed on an upper surface of a portion which is not oxidized. The conductors may be metal lines and/or bumps. The conductive structures may be solder balls.