Plasma Stabilizer for Stable Tungsten Etching
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Solution Overview
Problem
The challenge in etching thin metal layers, such as tungsten, in integrated circuits is maintaining plasma stability while avoiding ion bombardment, which can damage the substrate, especially when using fluorinated chemistry and increasing power or reducing the gap between the substrate and the chamber.
Innovation Solution
A spatially modified plasma is achieved using a plasma stabilizer with a substantially flat member having apertures, electrically isolated from the chamber, to control the ion and radical density ratio, allowing for a dense and stable plasma formation above the stabilizer and controlled plasma characteristics below it, reducing ion bombardment and enhancing etch uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If power is increased to maintain plasma stability, then plasma stability is improved, but ion bombardment of the substrate increases causing damage to the circuits
Solution Approach 1:
The plasma generation region is segmented from the substrate processing region using a plasma stabilizer plate with apertures. The plate divides the chamber into an upper plasma generation zone and a lower substrate processing zone, allowing independent control of plasma stability and ion flux to the substrate.
Solution Approach 2:
The plasma stabilizer plate acts as an intermediary component between the plasma source and the substrate. It mediates the plasma characteristics by filtering and redistributing charged and neutral species, enabling stable plasma maintenance without excessive ion bombardment damage.
2Stability of the object's composition
If the gap between the substrate and the chamber is decreased to maintain plasma stability, then plasma stability is improved, but ion bombardment of the substrate increases causing damage
Solution Approach 1:
The plasma stabilizer plate segments the chamber space, creating distinct plasma generation and processing zones. This allows the substrate to be positioned at an optimal distance from the plasma source while maintaining plasma stability through the plate's aperture structure.
3Productivity
If fluorinated chemistry is used to etch tungsten, then etching capability is improved, but plasma stability becomes difficult to maintain
Solution Approach 1:
The plasma stabilizer plate serves as an intermediary that decouples the fluorinated chemistry etching process from plasma stability requirements. It allows the use of reactive fluorinated gases for effective tungsten etching while maintaining stable plasma conditions through spatial separation and controlled species distribution.
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 enables stable plasma etching at lower pressures and power requirements, improving etch uniformity and selectivity, reducing substrate damage, and widening the process window for etching metals like tungsten, while maintaining the physical properties of the circuit structures.
Implementation Method 1
A plasma is utilized to enhance the etch process. However, it is difficult to maintain a stable plasma.
Implementation Method 2
An RF power source is provided for forming a plasma within the chamber.
Data Source
AI summary
A method and apparatus for etching a substrate using a spatially modified plasma is provided herein. In one embodiment, the method includes providing a process chamber having a plasma stabilizer disposed above a substrate support pedestal. A substrate is placed upon the pedestal. A process gas is introduced into the process chamber and a plasma is formed from the process gas. The substrate is etched with a plasma having an ion density to radical density ratio defined by the plasma stabilizer.