Plasma Processing Apparatus Edge Exclusion Reduction
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Solution Overview
Problem
Conventional plasma processing technologies face challenges in achieving uniform etching performance across the wafer surface, particularly at the outer peripheral edge, leading to non-uniformity and increased edge exclusion regions, which affect the quality and yield of semiconductor devices.
Innovation Solution
A plasma processing apparatus with a conductor ring outside the sample stage's periphery, covered by a dielectric material, where the height of the equipotential surface in the plasma ion sheath is set higher than the wafer top surface, ensuring the plasma ion sheath potential is produced solely by plasma generation, and the radio frequency bias power is uncoupled from the ring, maintaining a constant sheath thickness regardless of bias power variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional plasma processing apparatus is used, then the processing can be performed, but non-uniformity in etching rate appears between the central part and outer peripheral part of the wafer
Solution Approach 1:
The patent applies local quality by creating a non-uniform electric field distribution through a specifically designed electrode structure. The electrode has a convex shape with a curved surface that generates a non-uniform plasma ion sheath, making the electric field strength vary spatially across the wafer surface. This local variation in electric field quality compensates for the natural non-uniformity in plasma distribution, achieving uniform etching rates from the center to the outer peripheral regions of the wafer.
Solution Approach 2:
The patent changes the geometric parameters of the electrode, specifically designing it with a convex shape and controlled curvature radius. By adjusting the electrode's surface curvature and height distribution, the electric field parameters are modified to create a non-uniform field that compensates for plasma non-uniformity. This parameter optimization enables uniform ion incidence angles and etching rates across the entire wafer surface.
2Productivity
If the wafer outer peripheral part is processed, then more chips can be obtained, but the processed profile becomes non-uniform and falls out of the allowable range
Solution Approach 1:
The patent addresses edge region processing quality by applying local quality principles through the curved electrode surface. The electrode geometry is specifically designed to concentrate electric field lines toward the outer peripheral regions, ensuring that ion incidence angles remain perpendicular to the wafer surface even at the edges. This local field enhancement and direction control enables the outer peripheral part to be processed with the same precision as the center, expanding the usable wafer area and increasing chip yield.
Solution Approach 2:
The patent applies equipotentiality by carefully designing the electrode curvature to create regions of equal electric potential that ensure uniform ion acceleration across the wafer surface. The convex electrode shape generates equipotential surfaces that are parallel to the wafer, ensuring that ions incident on different regions (center and edge) experience similar acceleration conditions and maintain perpendicular incidence angles, thus achieving uniform profiles across the entire processing area.
3Device complexity
If a larger E.E. region is accepted, then the processing is simpler, but the price of the semiconductor device increases
Solution Approach 1:
The patent reduces the E.E. region size by changing the electric field parameters through optimized electrode geometry. By adjusting the electrode curvature radius and height distribution, the electric field is enhanced at the wafer edges, extending the perpendicular ion incidence region closer to the physical edge of the wafer. This parameter optimization reduces the E.E. region to 2 mm or less, maximizing the usable wafer area and reducing device cost without requiring complex additional processing steps.
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 configuration improves the uniformity of the etching performance by maintaining perpendicular ion incidence and reducing the edge exclusion region, enhancing the precision and yield of semiconductor device manufacturing by suppressing curvature and maintaining uniform etching rates across the wafer.
Implementation Method 1
generating plasma in the processing chamber
Implementation Method 2
applying a radio frequency bias to the sample stage
Implementation Method 3
the plasma ion sheath formed outside a sample outer periphery of the sample stage
Implementation Method 4
covered by a dielectric material
Data Source
AI summary
To improve processing uniformity by improving a working characteristic in an edge exclusion region. Provided is a plasma processing apparatus for processing a sample by generating plasma in a vacuum vessel to which a processing gas is supplied and that is exhausted to a predetermined pressure and by applying a radio frequency bias to a sample placed in the vacuum vessel, wherein a conductive radio frequency ring to which a radio frequency bias power is applied is arranged in a stepped part formed outside a convex part of the sample stage on which the wafer is mounted, and a dielectric cover ring is provided in the stepped part, covering the radio frequency ring, the cover ring substantially blocks penetration of the radio frequency power to the plasma from the radio frequency ring, and the radio frequency ring top surface is set higher than a wafer top surface.