Variable-Transmissivity Ion Beam Grid for Uniform Tilted Etching
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Solution Overview
Problem
In surface treatment processes using charged particle beams, such as ion beam etching, non-uniformity of etch features occurs when the substrate is tilted relative to the ion beam due to varying ion current density across the substrate area, caused by beam divergence and tilt angles, leading to inconsistent etch rates and feature quality.
Innovation Solution
A charged particle beam source with a grid assembly having varying transmissivity across its extent, where the transmissivity is lower at one extremity than the other, producing a non-uniform charged particle current density profile that compensates for the tilt of the substrate, ensuring a more uniform ion current density across the substrate area, thereby reducing non-uniformity in etch features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the substrate is tilted relative to the ion beam to form asymmetric slanted etch profiles, then the etch profile shape is improved, but the ion current density becomes non-uniform across the substrate area leading to non-uniform etch features
Solution Approach 1:
The grid assembly is designed with spatially varying transmissivity, where different regions of the grid have different aperture densities. Specifically, the region corresponding to the side of the substrate closer to the ion source has higher transmissivity (more apertures per unit area), while the opposite region has lower transmissivity. This local variation in grid structure compensates for the non-uniform ion current density caused by substrate tilt, ensuring uniform etch features across the entire substrate area.
Solution Approach 2:
The grid assembly introduces an asymmetric aperture distribution that mirrors the asymmetric geometry of the tilted substrate configuration. By making the grid structure itself asymmetric in terms of aperture density across its surface, the system compensates for the asymmetric ion beam incidence on the tilted substrate, thereby achieving uniform processing results despite the asymmetric setup.
2Shape
If the ion beam is used with a tilted substrate to achieve specific etch profiles, then the etch profile control is improved, but the ion current density varies across the substrate due to beam divergence
Solution Approach 1:
The grid assembly is designed with spatially varying transmissivity, where different regions of the grid have different aperture densities. Specifically, the region corresponding to the side of the substrate closer to the ion source has higher transmissivity (more apertures per unit area), while the opposite region has lower transmissivity. This local variation in grid structure compensates for the non-uniform ion current density caused by substrate tilt, ensuring uniform etch features across the entire substrate area.
3Ease of manufacture
If a uniform transmissivity grid is used, then the grid manufacturing is simple, but the ion current density becomes non-uniform when the substrate is tilted
Solution Approach 1:
The grid assembly is designed with spatially varying transmissivity, where different regions of the grid have different aperture densities. Specifically, the region corresponding to the side of the substrate closer to the ion source has higher transmissivity (more apertures per unit area), while the opposite region has lower transmissivity. This local variation in grid structure compensates for the non-uniform ion current density caused by substrate tilt, ensuring uniform etch features across the entire substrate area.
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 solution achieves improved uniformity of etched features across large substrates by intentionally varying the charged particle current density profile, reducing variations in etch rates and enhancing the quality and consistency of surface treatment processes, particularly for tilted substrates.
Implementation Method 1
a plasma generation unit adapted to convert an input gas within the plasma chamber into a plasma containing charged particles
Implementation Method 2
the one or more grids being electrically biased in use so as to accelerate charged particles from the plasma through the grid(s) to thereby output a charged particle beam
Data Source
AI summary
A charged particle beam source for a surface processing apparatus is disclosed. The charged particle beam source comprises: a plasma chamber; a plasma generation unit adapted to convert an input gas within the plasma chamber into a plasma containing charged particles; and a grid assembly adjacent an opening of the plasma chamber. The grid assembly comprises one or more grids each having a plurality of apertures therethrough, the one or more grids being electrically biased in use so as to accelerate charged particles from the plasma through the grid(s) to thereby output a charged particle beam, the major axis of which is substantially perpendicular to the plane of the grid assembly. The transmissivity of the or each grid to the charged particles is defined by the relative proportion of aperture area to non-aperture area, and at least one of the grids has a transmissivity which varies across the grid along a first direction, the transmissivity being lower adjacent a first extremity of the grid than adjacent a second extremity of the grid opposite the first extremity, the first direction lying parallel to the plane of the grid assembly, such that in use the charged particle beam output by the source has a non-uniform charged particle current density profile in a plane parallel to the plane of the grid assembly which varies along the first direction, the charged particle current density being lower adjacent a first edge of the beam than adjacent a second edge of the beam opposite the first edge.