Rotational Indexer Wafer Centering for Precise Pedestal Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor processing tools face challenges in accurately placing wafers due to positioning errors of wafers and pedestals, leading to reduced yield and degraded uniformity, as existing indexers cannot adjust for errors in wafer and pedestal alignment.
Innovation Solution
The implementation of a rotational indexer system with additional rotational axes and lateral movement capabilities, allowing for precise adjustment of wafer placement by rotating and translating the indexer arms relative to the pedestals, and using a controller to execute a series of steps for each wafer to center it on the destination pedestal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional rotational indexer is used to transfer wafers between processing stations, then wafer transfer efficiency is maintained, but positioning precision deteriorates due to accumulated errors from wafer slippage and pedestal misalignment
Solution Approach 1:
The indexer arm is divided into multiple independently controllable segments: the main indexer arm for radial movement, and an additional adjustable arm section with its own drive mechanism. This segmentation allows the distal end to be independently positioned to compensate for wafer placement errors without affecting the overall indexer structure.
Solution Approach 2:
The indexer arm transitions from a fixed rigid structure to a dynamically adjustable structure. The additional drive mechanism enables real-time adjustment of the arm's distal end position, allowing the system to adapt to and correct positioning errors during wafer transfer operations.
2Manufacturing precision
If wafers are transferred in unison on the indexer, then throughput is maintained, but the ability to correct positioning errors is lost
Solution Approach 1:
Instead of correcting the position of all wafers simultaneously, the system applies partial correction only to the distal end of the indexer arm where the wafer is released. This localized adjustment is sufficient to ensure accurate wafer placement while maintaining synchronized transfer of all wafers through the system.
3Manufacturing precision
If additional adjustment mechanisms are added to the indexer arm, then positioning precision is improved, but device complexity increases
Solution Approach 1:
The additional drive mechanism serves multiple functions: it adjusts the distal end position for error compensation, maintains synchronization with the main indexer rotation, and can potentially accommodate different wafer sizes. This multi-functionality justifies the added complexity by providing versatile positioning capabilities.
Data Source
AI summary
Rotational indexers are provided that allow for wafer-by-wafer centering to be performed in association with each wafer pedestal-to-pedestal transfer operation within a multi-station chamber. One such rotational indexer has a rotational center axis that is movable along one or more lateral directions in order to provide wafer centering capability; sealing arrangements with lateral movement capability are provided for such implementations. Another such rotational indexer uses additional rotational capability at the wafer supports of the indexer, in combination with deliberate off-center placement of the wafers on the wafer supports of the indexer, to provide wafer centering capability.