Ion Implantation Wafer Scan and Rotation Control
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Solution Overview
Problem
Conventional ion implantation methods face challenges in achieving uniform implantation on larger wafers due to difficulties in maintaining beam uniformity and the complexity of simultaneous movement and rotation, which can lead to wafer damage and decreased throughput.
Innovation Solution
The method involves moving and rotating the wafer such that the ion beam length is equal to or greater than the wafer diameter, allowing for slower rotation velocities and adjustable movement velocities to ensure uniform implantation, with optional tilting and error correction mechanisms to maintain uniformity and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the ion beam length is increased to cover larger wafers, then the wafer coverage is improved, but the beam uniformity deteriorates
Solution Approach 1:
The patent applies dynamics by making the wafer rotation velocity variable rather than constant. The rotation velocity is adjusted based on the radial position of different wafer regions, with slower rotation at the periphery and faster rotation at the center. This dynamic adjustment compensates for the non-uniform beam intensity distribution, allowing the entire wafer surface to be covered while maintaining uniform implantation dosage.
2Reliability
If the rotation velocity is increased to ensure complete wafer implantation, then the implantation completeness is improved, but the wafer damage increases
Solution Approach 1:
The patent applies local quality by making the rotation velocity dependent on the radial position across the wafer surface. Different regions of the wafer rotate at different velocities: the periphery rotates slower while the center rotates faster. This localized velocity adjustment ensures that all regions receive adequate implantation exposure while preventing excessive mechanical stress and damage that would result from uniform high-speed rotation.
3Manufacturing precision
If the simultaneous movement and rotation is implemented for uniform implantation, then the implantation uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent applies the taking out principle by separating the simultaneous movement and rotation into distinct operational phases. Rather than requiring complex coordinated control of both movements occurring at the same time, the system performs wafer rotation first to achieve uniform angular distribution, then executes linear movement across the beam. This temporal separation simplifies the control mechanism while maintaining implantation uniformity.
4Manufacturing precision
If the movement velocity is adjusted to compensate for projection ratio differences, then the implantation uniformity is improved, but the control complexity increases
Solution Approach 1:
The patent applies copying by using a pre-calculated velocity profile that replicates the optimal speed adjustments needed for uniform implantation. Instead of requiring real-time complex calculations and adaptive control, the system uses a predetermined velocity pattern that has been optimized in advance. This copied velocity profile simplifies the control system while achieving the desired uniformity compensation for different radial positions.
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 avoids wafer damage and complexity by ensuring uniform ion implantation across the wafer surface with slower rotation velocities and flexible movement profiles, improving implantation uniformity and throughput while allowing for precise adjustment of implantation results.
Implementation Method 1
An ion implantation process typically requires a uniform and consistent dose or amount of ions to be implanted into a wafer
Data Source
AI summary
Initially, an ion beam is formed as an elongated shape incident on a wafer, where the shape has a length along a first axis longer than a diameter of the wafer, and a width along a second axis shorter than the diameter of the wafer. Then, a center of the wafer is moved along a scan path intersecting the ion beam at a movement velocity, and the wafer is rotated around at a rotation velocity simultaneously. During the simultaneous movement and rotation, the wafer is totally overlapped with the ion beam along the first axis when the wafer intersects with the ion beam, and the rotation velocity is at most a few times of the movement velocity. Both the movement velocity and the rotation velocity can be a constant or have a velocity profile relative to a position of the ion beam across the wafer.