Scanning Ion Beam Etch with Asymmetric Wafer Scan Compensation
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Solution Overview
Problem
Ion beam etching processes face asymmetry issues between the inboard and outboard sides of devices on a wafer due to beam divergence and tilt angles, leading to non-uniform etching, especially when using small ion sources and grids, which complicates achieving symmetrical features.
Innovation Solution
Implementing asymmetric scanning velocity and modulating ion beam flux during the etching process to correct asymmetry, either by varying scan velocity or adjusting ion beam current/voltage, allowing for uniform etching across the wafer even with smaller ion sources and grids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If small ion sources and grids are used, then device complexity and cost are reduced, but manufacturing precision deteriorates due to beam divergence causing inboard-outboard asymmetry
Solution Approach 1:
The patent implements dynamic scanning motion of the wafer across the ion beam, transitioning from static exposure to dynamic scanning. The wafer moves through the beam path in a scanning motion that allows different regions to be exposed sequentially, correcting the asymmetry caused by beam divergence while using compact ion sources.
Solution Approach 2:
The patent introduces asymmetric scanning velocity profiles where the wafer moves at different speeds during different portions of the scan cycle. By varying the scan velocity asymmetrically, the system compensates for the inherent beam divergence asymmetry, achieving uniform etching across the wafer surface despite using small ion sources.
2Manufacturing precision
If wafer scanning is implemented to correct asymmetry, then manufacturing precision improves, but productivity decreases due to additional scan time
Solution Approach 1:
The patent implements continuous scanning motion without interruption, where the wafer continuously moves through the ion beam in a scanning pattern. This continuous action eliminates idle time between exposures and maintains productive etching throughout the entire scan cycle, achieving both precision and efficiency.
Solution Approach 2:
The patent employs periodic scanning cycles where the wafer repeatedly scans across the ion beam in a controlled periodic manner. This periodic action allows optimization of scan parameters to achieve uniform etching while maintaining reasonable processing throughput through efficient cycle management.
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 ensures uniform etching across the wafer by compensating for beam divergence and tilt-related asymmetries, maintaining overall uniformity even with smaller ion sources and grids, and can be achieved through single or multiple scans with linear or curved motion paths.
Implementation Method 1
Ion source 105 can be comprised of a plasma chamber 110
Implementation Method 2
Ion extraction grid system 150 extracts and helps collimate ion beamlets coming out of each of the holes of the plates
Implementation Method 3
In an IBE process, wafer 180 is placed in front of an ion source 105. At least one surface of the wafer 180 can be exposed to a beam 130
Implementation Method 4
The energy of the ions extracted from the ion source 105 is defined by the voltages applied to the grid system 150
Data Source
AI summary
The present disclosure provides a method to adjust asymmetric velocity of a scan in a scanning ion beam deposition or etch process to correct asymmetry of depositing or etching between the inboard side and the outboard side of device structures on a wafer, while maintaining the overall uniformity of the respective deposition or etch across the full wafer.