Oscillating Ion Beam Scan Pattern for Uniformity
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Solution Overview
Problem
Conventional ion implantation techniques face challenges in achieving uniform ion beam distribution due to ion beam noise, which can be mitigated by increasing the number of incremental applications of the ion beam, but existing methods are optimized for throughput and may not provide additional ways to reduce noise impact.
Innovation Solution
An oscillating scan pattern is implemented, where the ion beam is oscillated when incident on the workpiece, increasing the number of 'touches' on the surface and averaging out noise fluctuations, using a combination of beam scanning and workpiece movement to create a modified zig-zag or oscillating pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of incremental applications of the ion beam is increased to average out ion beam noise, then manufacturing precision is improved, but device complexity and setup time increase
Solution Approach 1:
The patent applies periodic action by implementing an oscillating scan pattern where the ion beam repeatedly traverses the same wafer region in a periodic manner. The beam oscillates between opposite edges of the wafer multiple times, creating periodic passes over each location. This periodic repetition allows statistical averaging of ion beam noise fluctuations, improving dose uniformity without requiring complex multi-parameter adjustments.
Solution Approach 2:
The patent employs dynamics by transitioning from a static conventional scan pattern to a dynamic oscillating pattern. The scan pattern dynamically adjusts the beam trajectory to oscillate back and forth across the wafer surface, creating multiple overlapping passes. This dynamic approach increases the number of incremental applications to each location while maintaining simple control logic, resolving the contradiction between precision improvement and complexity increase.
2Manufacturing precision
If the number of incremental applications is increased by slowing wafer movement or increasing beam scanning frequency, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The oscillating scan pattern creates periodic passes over each wafer location, with the beam traveling back and forth multiple times. This periodic action increases the number of incremental dose applications to each point, averaging out noise fluctuations and improving uniformity. Crucially, this is achieved without slowing overall wafer throughput because the oscillation occurs within the existing scan cycle framework.
Solution Approach 2:
The patent introduces a temporal dimension to the scan pattern by oscillating the beam trajectory within the existing spatial scan path. Instead of simply moving slower or increasing frequency in one dimension, the oscillation adds a time-varying component to the beam position, creating multiple passes over the same area within the same overall processing time, thus maintaining productivity while improving precision.
3Manufacturing precision
If tighter restraints on permissible ion beam noise are placed during set-up, then manufacturing precision is improved, but loss of time increases due to longer set-up times
Solution Approach 1:
The patent converts the harmful effect of ion beam noise into a beneficial averaging process. Instead of trying to eliminate noise through tight restraints and lengthy set-up procedures, the oscillating scan pattern embraces the noise fluctuations and uses repeated periodic passes to statistically average them out. This approach achieves high uniformity without requiring time-consuming set-up adjustments, reducing set-up time while maintaining precision.
Solution Approach 2:
The patent changes the scan pattern parameter from a conventional single-pass trajectory to a multi-pass oscillating trajectory. This parameter change transforms how the beam interacts with the wafer, creating multiple incremental applications per location. The result is that noise averaging occurs automatically through the pattern design itself, eliminating the need for time-consuming set-up adjustments and tight noise restraints.
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 enhances the uniformity of ion implantation by increasing the number of ion beam interactions with the workpiece, allowing for tighter noise restraints and potentially shorter setup times and higher throughput.
Implementation Method 1
A desired impurity material may be ionized in an ion source, the ions may be accelerated to form an ion beam of prescribed energy, and the ion beam may be directed at a front surface of the wafer
Data Source
AI summary
An ion implanter includes an ion beam generator configured to generate an ion beam and direct the ion beam towards a workpiece, wherein relative motion between the ion beam and the workpiece produces a scan pattern on a front surface of said workpiece. The scan pattern has an oscillating pattern on at least a portion of said front surface of said workpiece.