Polymer Layer Edge Protection for Semiconductor Etch
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Solution Overview
Problem
Conventional semiconductor wafer fabrication processes face issues with thermal damage and alignment accuracy due to the close proximity of polyimide film openings to dicing streets during laser cutting, leading to device failures and yield issues, and enlarging dicing streets or using two-step masking processes do not adequately address these problems.
Innovation Solution
A method involving the application of a polymer layer, such as polyimide, to a passivation structure with openings patterned to have edges pulled back from dicing streets, allowing the polymer layer to serve as an etch mask while reducing thermal damage risks during laser trenching and mechanical sawing, maintaining accurate alignment with underlying conductor pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the polyimide film openings are positioned in vertical alignment with the underlying edges of the dicing street to achieve accurate bump alignment, then the alignment accuracy between bumps and conductor pads is improved, but the polyimide film is subjected to thermal damage or burning during the laser cutting operation
Solution Approach 1:
The patent segments the opening structure into multiple parts: the main opening body and an extended portion that reaches toward the dicing street. This segmentation allows the main opening to maintain accurate alignment for bump positioning while the extended portion serves as a thermal buffer zone that absorbs laser heat without affecting the alignment-critical regions
Solution Approach 2:
The extended portion of the opening acts as an intermediary element between the main opening and the dicing street. It absorbs the thermal energy from laser cutting through ablation, protecting the polyimide film edges and ensuring that thermal damage does not compromise the alignment accuracy between bumps and conductor pads
2Object-affected harmful factors
If the width of dicing streets is enlarged to provide polyimide edge pull back from dicing street edges, then the risk of thermal damage to the polyimide film is reduced, but the gross die per wafer decreases
Solution Approach 1:
Instead of solving the thermal damage problem by increasing the horizontal dimension (dicing street width), the patent introduces a vertical dimension solution through the extended opening portion. This allows the dicing street to maintain its original width for maximum die density while the extended opening provides the necessary thermal buffer zone for laser cutting protection
3Object-affected harmful factors
If a two-step process is used involving first masking the passivation layer and etching followed by polyimide coating, then the polyimide edge pull back is achieved, but accurate alignment between bumps and underlying conductor pads cannot be provided
Solution Approach 1:
The patent performs preliminary action by forming the extended opening portion in the polyimide film before the dicing operation. This pre-formed structure serves both as a thermal buffer during laser cutting and as a reference feature that maintains accurate alignment relationships, eliminating the need for subsequent two-step masking processes that compromise alignment precision
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 reduces the risk of thermal damage to the polymer film and maintains accurate alignment between bumps and conductor pads, enhancing the reliability and yield of semiconductor chip fabrication by using the polymer layer as an etch mask with edges set back from dicing streets.
Implementation Method 1
A first opening is patterned in the polymer layer with opposing edges pulled back from the dicing street. A mask is applied over the first opening. A first portion of the passivation structure is etched while using the polymer layer as an etch mask.
Implementation Method 2
Since certain conventional dicing processes employ a two-step process that involves a first laser trench cutting process followed by a mechanical sawing process, the close proximity of the polyimide dicing street opening edges to the dicing street edges can create the risk of thermal damage or burning of the polyimide film during the laser cutting operation.
Implementation Method 3
Dicing saws are made with great care and operate more precisely than a comparable masonry circular saw. At the conclusion of the processing steps to form the individual dice, a so-called dicing or sawing operation is performed on the wafer to cut out the individual dice.
Data Source
AI summary
Various semiconductor workpiece polymer layers and methods of fabricating the same are disclosed. In one aspect, a method of manufacturing is provided that includes applying a polymer layer to a passivation structure of a semiconductor workpiece where the semiconductor workpiece has first and second semiconductor chips separated by a dicing street. A first opening is patterned in the polymer layer with opposing edges pulled back from the dicing street. A mask is applied over the first opening. A first portion of the passivation structure is etched while using the polymer layer as an etch mask.