Angled Ion Beam Planarization of Polycrystalline Tungsten
Solution Overview
Problem
Conventional thin film processing techniques, such as CMP and ion-based methods, face challenges in achieving flatness across wafers, leading to issues like dishing, erosion, and surface roughness, particularly when dealing with polycrystalline layers like tungsten, which affect semiconductor device manufacturing yields and thickness measurements.
Innovation Solution
A method involving the directional and rotational use of an ion beam with a non-zero angle of incidence relative to the substrate plane, combined with scanning, to etch and planarize polycrystalline layers, reducing surface roughness and maintaining smoothness by varying the twist angle and exposure cycles, thereby canceling out facet-dependent etch-rate dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ion beam processing is used to remove polycrystalline material, then material removal efficiency is improved, but surface roughness increases due to facet-dependent sputter yields
Solution Approach 1:
The substrate is rotated during ion beam exposure to dynamically change the incident angle of ions relative to crystal facets. This rotation ensures that no single facet orientation is consistently exposed to the ion beam, thereby averaging out the facet-dependent sputter yields and preventing roughness formation while maintaining efficient material removal
Solution Approach 2:
The incident angle of the ion beam is changed from normal incidence to an angled incidence (e.g., 45 degrees). This parameter change modifies the sputtering dynamics to reduce the sensitivity to facet orientation, thereby decreasing surface roughness while maintaining acceptable material removal rates
2Manufacturing precision
If CMP is used to planarize thin films, then material planarization is achieved, but dishing and erosion occur along with chemical selectivity issues
Solution Approach 1:
The mechanical CMP process is replaced with a physical ion beam sputtering process. This substitution eliminates the mechanical contact that causes dishing and erosion, using instead a controlled ion-matter interaction that can be precisely tuned through angle and rotation parameters to achieve planarization without the harmful side effects of CMP
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 planarizes and smooths polycrystalline layers without increasing surface roughness, improving semiconductor device manufacturing yields and enabling accurate thickness measurements, while avoiding the limitations of conventional methods like CMP and uniform ion etching.
Implementation Method 1
Known processing techniques using ions may, while removing polycrystalline material in particular, generate unwanted levels of surface roughness of the film being treated
Data Source
AI summary
A method of processing a layer. The method may include providing the layer on a substrate, the substrate defining a substrate plane; directing an ion beam to an exposed surface of the layer in an ion exposure when the substrate is disposed in a first rotational position, the ion beam having a first ion trajectory, the first ion trajectory extending along a first direction, wherein the first ion trajectory forms a non-zero angle of incidence with respect to a perpendicular to the substrate plane; performing a rotation by rotating the substrate with respect to the ion beam about the perpendicular from the first rotational position to a second rotational position; and directing the ion beam to the exposed surface of the layer in an additional ion exposure along the first ion trajectory when the substrate is disposed in the second rotational position.