Shadow Ring Height Control for Wafer Edge Plasma Etching
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Solution Overview
Problem
The edge portion of a wafer is damaged during plasma etching due to excessive plasma in existing dry etching processes.
Innovation Solution
A dry etching apparatus with a shadow ring and distance control unit that adjusts the vertical distance between the edge ring and shadow ring to prevent excessive plasma exposure, using a lift pin and fixing pins to manage the shadow ring's position, thereby controlling the etching rate and reducing unwanted overetching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is performed using a conventional dry etching apparatus, then the etching process can be completed, but the edge portion of the wafer is damaged by excessive plasma
Solution Approach 1:
A shadow ring is introduced as an intermediary component between the plasma source and the wafer edge. The shadow ring casts a shadow that blocks excessive plasma from reaching the wafer edge portion, thereby protecting it from damage while allowing the etching process to continue on the main wafer surface
Solution Approach 2:
The protection mechanism is segmented by positioning the shadow ring at a specific height above the wafer surface. This creates a spatial segmentation where the upper region is protected from excessive plasma by the shadow ring's shadow, while the etching process continues in the lower region
2Reliability
If the shadow ring is positioned closer to the wafer, then edge protection is improved, but the etching rate may be affected
Solution Approach 1:
The shadow ring's vertical position is made adjustable rather than fixed. The operation unit can raise and lower the shadow ring to different heights, allowing dynamic optimization of the balance between edge protection effectiveness and etching rate based on specific process requirements
3Device complexity
If the shadow ring position is fixed, then the structure is simple, but the etching rate cannot be adjusted
Solution Approach 1:
The shadow ring positioning system is designed with dynamic adjustability through the operation unit that can raise and lower the shadow ring. This allows the etching rate to be controlled by adjusting the shadow ring height, providing versatility while maintaining relatively simple structural implementation
Solution Approach 2:
The vertical position parameter of the shadow ring is made variable. By changing this parameter (height above wafer surface), the etching rate can be adjusted to match different process requirements, transforming a static structure into an adaptable system
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 solution effectively prevents damage to the edge portion of the wafer, enhancing the reliability and productivity of the etching process by adjusting the etching rate through controlled vertical distance management.
Implementation Method 1
a plasma etching process is a type of the dry etching process. The plasma etching process has a feature of etching a layer to be etched on a wafer by using plasma generated by injecting a process gas into a process chamber
Data Source
AI summary
Provided is a dry etching apparatus including: a plasma process chamber; an edge ring which is arranged in the plasma process chamber and on which a wafer is mounted; a shadow ring positioned to be spaced apart by a first vertical distance above the edge ring during a plasma etching process of the wafer; an operation unit coupled to the shadow ring and having a lift pin that raises and lowers the shadow ring; a fixing portion having a plurality of fixing pins engaged with the lift pin at different positions to fix a lowering point of the shadow ring; and a distance control unit that controls the fixing portion to determine the first vertical distance, wherein the first vertical distance is determined by a first horizontal distance between the wafer and the edge ring.