Plasma Doping Cover Ring Structure for Carbon Contamination Mitigation
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Solution Overview
Problem
Plasma doping systems face contamination issues due to carbon atoms being sputtered from the shield ring during ion implantation, which contaminates the semiconductor wafer, necessitating a solution to mitigate this while preserving the functionality of the shield ring.
Innovation Solution
A cover ring with a crystalline base layer and a non-crystalline top layer is introduced to mitigate sputtering of the shield ring, specifically formed with materials like silicon or silicon nitride to prevent carbon contamination, and is designed to be easily replaceable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a shield ring is used to extend the plasma sheath beyond the wafer edge, then plasma sheath extension is improved, but carbon contamination increases due to sputtering of the shield ring
Solution Approach 1:
A cover ring is introduced as an intermediary component between the ion beam and the shield ring. The cover ring absorbs the ion bombardment that would otherwise sputter carbon from the shield ring, while allowing the shield ring to maintain its function of extending the plasma sheath beyond the wafer edge.
Solution Approach 2:
The cover ring is designed as a replaceable, consumable component that can be easily replaced after use. This allows the use of materials optimized for sputter resistance without concern for long-term durability, as the cover ring can be discarded and replaced when degraded, while the expensive shield ring remains protected.
2Strength
If the shield ring is made of silicon carbide, then structural integrity is improved, but sputter resistance deteriorates
Solution Approach 1:
The shielding function is segmented into two separate components: the shield ring provides structural integrity and plasma sheath extension, while the cover ring provides sputter resistance. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
The cover ring is made from materials specifically selected for their resistance to ion sputtering, such as amorphous carbon, diamond-like carbon, or silicon nitride. These materials form a protective composite structure that prevents carbon contamination while allowing the underlying silicon carbide shield ring to maintain its structural properties.
3Object-generated harmful factors
If a cover ring is added to protect the shield ring, then carbon contamination is reduced, but device complexity increases
Solution Approach 1:
The cover ring is designed as a simple, inexpensive, replaceable component that can be quickly installed and removed. This minimizes the operational complexity despite the additional part, as the cover ring can be swapped without requiring complex tooling or procedures.
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
The cover ring effectively reduces carbon contamination of the wafer by blocking accelerated ions from striking the shield ring, thereby improving the quality of the implantation process and being easily replaceable to maintain process integrity.
Implementation Method 1
a plasma source for producing a plasma having a plasma sheath in a vicinity of the workpiece, the plasma containing positive ions of the ionizable gas, and accelerating said positive ions across the plasma sheath toward the platen for implantation into the workpiece
Implementation Method 2
The applied voltage causes ions in the plasma to cross the plasma sheath and to be implanted into the wafer
Implementation Method 3
a cover ring disposed on top of the shield ring and adapted to mitigate sputtering of the shield ring
Data Source
AI summary
A plasma doping system including a plasma doping chamber, a platen mounted in the plasma doping chamber for supporting a workpiece, a source of ionizable gas coupled to the chamber, the ionizable gas containing a desired dopant for implantation into the workpiece, a plasma source for producing a plasma having a plasma sheath in a vicinity of the workpiece, the plasma containing positive ions of the ionizable gas, and accelerating said positive ions across the plasma sheath toward the platen for implantation into the workpiece, a shield ring surrounding the platen and adapted to extend the plasma sheath beyond an edge of the workpiece, and a cover ring disposed on top of the shield ring and adapted to mitigate sputtering of the shield ring, wherein the cover ring comprises a crystalline base layer and a non-crystalline top layer.