Semiconductor Wafer Dicing with Polymer Coating to Remove Fluorine Contamination
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Solution Overview
Problem
The semiconductor wafer dicing process using fluorine-based chemistry in plasma etching often results in residual fluorine contamination, leading to corrosion of metal contact openings, poor soldering adhesion, and high electrical contact resistance, causing premature failure due to fluorine diffusion and propagation.
Innovation Solution
A semiconductor wafer dicing process involving a polymer coating on the wafer, followed by plasma etching and subsequent exposure to an oxygen plasma to remove the outermost contaminated layer, with a residual polymer coating left to protect the wafer, and finally removing the coating using a wet technique to minimize fluorine contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorine-based chemistry is used in plasma etching to dice wafers, then the dicing efficiency and physical integrity of dies are improved, but residual fluorine contamination causes corrosion of metal contact openings and poor soldering adhesion
Solution Approach 1:
A polymer coating is applied to the wafer surface before plasma etching to serve as a protective barrier. This preliminary protective measure prevents fluorine from the etching process from contaminating the wafer and metal contact openings, thereby maintaining soldering adhesion while preserving dicing efficiency
Solution Approach 2:
The polymer coating acts as an intermediary layer between the fluorine-based plasma etching process and the wafer surface. It absorbs and blocks the harmful fluorine species, allowing the etching to proceed efficiently while protecting the underlying metal structures from contamination
2Area of stationary object
If fluorine-based plasma etching is used to separate individual dies, then the scribe channel width is reduced and more die can be occupied per wafer, but fluorine diffusion through the coating causes metal corrosion and high electrical contact resistance
Solution Approach 1:
The polymer coating parameters (thickness, composition, cross-linking density) are optimized to provide sufficient barrier properties against fluorine diffusion while maintaining the narrow scribe channel benefits. The coating is designed with specific physical and chemical properties that prevent fluorine penetration at the required etching dimensions
Solution Approach 2:
A composite structure is created with the polymer coating layered over the wafer surface. This composite provides both the protective function against fluorine contamination and allows the underlying etching process to achieve narrow scribe channels, combining the benefits of protection and precision
3Object-affected harmful factors
If the polymer coating is completely removed after plasma etching, then all fluorine contamination is eliminated, but the wafer surface becomes directly exposed to residual fluorine in the chamber
Solution Approach 1:
Instead of completely removing the polymer coating, a partial removal approach is used where the coating is retained to a thickness that provides sufficient protection against residual fluorine. This partial action maintains the protective function while allowing the etching process to complete, avoiding the risk of direct exposure that would occur with complete removal
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 process significantly reduces fluorine contamination, improving the integrity and adhesion of solder bonds, and extending the lifespan of the semiconductor dies by maintaining a low fluorine-to-oxygen ratio, thus preventing premature failure.
Implementation Method 1
The coating provides a protective layer for the laser scribe process and acts to protect the wafer surface by preventing direct exposure to the process plasma and thus minimises fluorine based metal corrosion and contamination of the wafer
Implementation Method 2
exposing the processed product, wafer frame and tape to an oxygen plasma within the chamber, to partially remove an outermost region of the polymer coating which is most heavily contaminated with fluorine
Implementation Method 3
During the plasma etching process it is common to use fluorine based chemistry to etch silicon wafers
Implementation Method 4
U.S. Pat. No. 5,501,893 discloses a cyclic etch process, commonly described as the Bosch process, for silicon wafer dicing using SF6 and Ar gas in the etch cycle
Implementation Method 5
the polymer coating is heated to a temperature between 40° C. and 150° C. It is found that baking the polymer coating further reduces the ability of fluorine to diffuse and propagate through the coating
Data Source
AI summary
A semiconductor wafer dicing process is disclosed for dicing a wafer into individual dies. Scribe lines are formed within a polymer coating to expose regions of wafer to form a pre-processed product. The pre-processed product within the chamber is plasma etched to remove the exposed regions of the wafer to separate the individual dies and form a processed product. A frame cover is then removed and the processed product, wafer frame and adhesive tape are exposed to an oxygen plasma within the chamber to partially remove an outermost region of the polymer coating, which is most heavily contaminated with fluorine, to leave a residual polymer coating on the individual dies and form a post-processed product. The residual polymer coating on the individual dies of the post-processed product is then removed.