Uniformity Control Circuit for Plasma Etch Impedance Matching
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Solution Overview
Problem
In semiconductor wafer fabrication, achieving uniformity in plasma etching is challenging due to the difficulty and costliness of manipulating electrode shapes and gas flows in plasma etch chambers, which affects etch rate and impedance control.
Innovation Solution
A uniformity control circuit (UCC) is integrated within an impedance matching circuit (IMC) to adjust capacitance, allowing for manual or actuator-controlled changes to achieve radial plasma uniformity, isolation from megahertz signals, and desired power delivery, replacing the need for costly electrode shape modifications and gas flow adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrode shapes are manipulated to control plasma impedance and achieve uniform etching, then etch rate uniformity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces a uniformity control circuit as an intermediary device between the power source and the plasma chamber. This circuit, containing adjustable capacitive elements, mediates the power delivery to achieve uniform plasma distribution without requiring complex electrode shape modifications. The intermediary circuit handles the complexity of uniformity control separately from the electrode design.
Solution Approach 2:
The patent replaces the mechanical approach of manipulating electrode shapes and positions with an electrical approach using a uniformity control circuit. Instead of physically adjusting electrode geometry to achieve uniform plasma, the system uses adjustable capacitive elements in an electrical circuit to control power distribution and achieve the same uniformity goal through electrical means.
2Manufacturing precision
If gas flow is adjusted to control plasma uniformity, then etch rate distribution is improved, but system complexity and operational difficulty increase
Solution Approach 1:
The patent replaces the operational complexity of manually adjusting gas flows with an automated electrical control system. The uniformity control circuit with adjustable capacitive elements provides a straightforward electrical interface for controlling plasma uniformity, eliminating the need for complex gas flow manipulation and making the system easier to operate.
3Manufacturing precision
If electrode positioning is changed to control plasma distribution, then radial uniformity is improved, but device complexity and maintenance cost increase
Solution Approach 1:
The patent introduces a uniformity control circuit as an intermediary that handles the complexity of radial uniformity control. This electrical intermediary, containing adjustable capacitive elements, replaces the need for complex mechanical electrode positioning mechanisms. The intermediary circuit provides a simpler interface for achieving the same uniformity goal.
Solution Approach 2:
The patent substitutes mechanical electrode positioning systems with an electrical uniformity control circuit. Instead of using motors, actuators, or mechanical adjustment mechanisms to position electrodes for radial uniformity, the system uses an electrical circuit with adjustable capacitive elements to achieve the same effect through electrical parameter control.
4Manufacturing precision
If complex electrode designs are used to achieve plasma uniformity, then etch rate control is improved, but ease of repair and replacement deteriorate
Solution Approach 1:
The patent introduces a uniformity control circuit as a replaceable intermediary device that simplifies repair and maintenance. Instead of requiring replacement or modification of complex electrode structures, the uniformity control circuit can be independently adjusted or replaced to maintain etch rate control performance.
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 UCC enables cost-effective and efficient control of etch rate uniformity and power delivery, simplifying the process while maintaining effective impedance matching, thereby improving plasma processing efficiency.
Implementation Method 1
The UCC is connected serially along the path of the first circuit to define a capacitance that at least partially influences a radial uniformity profile in an etch rate produced by the plasma chamber
Implementation Method 2
radio frequency (RF) power is applied to one or more electrodes, e.g., an upper electrode, a lower electrode, etc., in the plasma etch chamber
Implementation Method 3
Upon applying a desired amount of the RF power to the electrodes, the process gases in the plasma etch chamber are ionized such that plasma is created within a gap between the upper and lower electrodes
Data Source
AI summary
An impedance matching circuit (IMC) is described. The IMC includes a first circuit that includes a first plurality of tuning elements defined along a path. The first circuit has an input coupled to a kilohertz (kHz) radio frequency (RF) generator. The first circuit is coupled to an output. The IMC further includes a second circuit having a second plurality of tuning elements. The second circuit has an input coupled to a megahertz (MHz) RF generator and is coupled to the output. The IMC includes a uniformity control circuit (UCC) defined from at least one of the plurality of tuning elements of the first circuit. The UCC is connected serially along the path of the first circuit to define a capacitance that at least partially influences a radial uniformity profile in an etch rate produced by a plasma chamber.