Inductively Coupled Plasma Pedestal Height Control
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Solution Overview
Problem
Conventional inductively coupled plasma reactors face challenges in maintaining uniform plasma ion density across larger semiconductor substrates, leading to non-uniform processing results, particularly at the edge regions, known as edge-drop.
Innovation Solution
The apparatus and method involve a substrate supporting pedestal with a height difference between the top surface and the edge surface to control the exposure of the edge region to the process gas, allowing for adjustable edge performance by varying the height difference to achieve uniform plasma distribution and processing across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional inductively coupled plasma reactors are used with standard substrate support, then the plasma ion density distribution becomes non-uniform across the substrate surface, but the device structure remains simple and easy to manufacture
Solution Approach 1:
The substrate support structure incorporates a raised central region that creates different heights at different locations on the support surface. This local variation in height causes the substrate to be positioned at different distances from the plasma source across its surface, thereby creating localized differences in plasma ion density exposure that compensate for the natural radial non-uniformity of the plasma field.
Solution Approach 2:
The invention introduces a vertical dimension (height variation) to the otherwise two-dimensional substrate support surface. By raising the central region vertically, the patent creates a three-dimensional substrate support structure that exploits the vertical distance parameter to control plasma ion density distribution, transforming a planar problem into a spatial solution.
2Area of stationary object
If the substrate size is increased to process larger wafers, then the processing capacity is improved, but maintaining uniform plasma ion density across the entire substrate surface becomes more difficult
Solution Approach 1:
The raised central region design creates zones of different plasma exposure across the substrate surface. The central raised area positions the middle portion of large substrates closer to the plasma source, increasing ion density in that region, while the peripheral areas remain at the original height, maintaining lower ion density. This local differentiation compensates for the natural decrease in plasma density toward the edges of large substrates.
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 effectively reduces edge-drop by ensuring uniform exposure of the edge region to the process gas, enhancing the uniformity of processing results, such as nitrogen dosage, across the substrate surface.
Implementation Method 1
Conventional inductively coupled plasma reactors generally includes a vacuum chamber having a side wall and a ceiling, a workpiece support pedestal within the chamber and generally facing the ceiling, a gas inlet capable of supplying a process gas into the chamber, and one or more coil antennas overlying the ceiling. The one or more coil antennas are generally wound about an axis of symmetry generally perpendicular to the ceiling. A RF plasma source power supply is connected across each of the coil antennas. Sometimes, the reactor may include an inner coil antenna overlying the ceiling and surrounded by an outer coil antenna.
Implementation Method 2
The power of the signal applied to the coil antenna primarily determines the plasma ion density within the chamber, while the power of the bias signal applied to the substrate determines the ion energy at the wafer surface.
Data Source
AI summary
The present invention generally provides methods and apparatus for controlling edge performance during process. One embodiment of the present invention provides an apparatus comprising a chamber body defining a process volume, a gas inlet configured to flow a process gas into the process volume, and a supporting pedestal disposed in the process volume. The supporting pedestal comprises a top plate having a substrate supporting surface configured to receive and support the substrate on a backside, and an edge surface configured to circumscribe the substrate along an outer edge of the substrate, and a height difference between a top surface of the substrate and the edge surface is used to control exposure of an edge region of the substrate to the process gas.