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A Method for Improved WIP Balance in Wafer Fabrication by dynamically altering lot priorities based on a WIP distribution Advocate which monitors and analyses WIP position

IP.com Disclosure Number: IPCOM000132019D
Original Publication Date: 2005-Nov-29
Included in the Prior Art Database: 2005-Nov-29
Document File: 3 page(s) / 26K

Publishing Venue

IBM

Abstract

This invention is a method to enhance the level of intelligence in manufacturing dispatch that results in improved WIP positioning or balancing within the production wafer fabrication process. Typically within the wafer fabrication process WIP imbalances result from a wide variety of sources inherent in the manufacturing process: differences in down time distributions and availability, local optimization from a focus on batch sizes and trains, imbalanced interruptions of production wafer throughput to handle development lots, and start profiles. This imbalance generates lost production opportunities from starved tools, excessive tardiness of lots due to poor pacing, and a whipsaw effect in output. This method develops and advocates explicit actions in assigning a lot to a tool (what next dispatch decision) to maintain balance or put in place a path to recovered balance while adjusting for short term output needs and intrinsic throughput characteristics of tools.

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A Method for Improved WIP Balance in Wafer Fabrication by dynamically altering lot priorities based on a WIP distribution Advocate which monitors and analyses WIP position

This article describes a method to enhance the level of intelligence in manufacturing dispatch that results in improved WIP positioning or balancing within the production wafer fabrication process. Typically within the wafer fabrication process WIP imbalances result from a wide variety of sources inherent in the manufacturing process: differences in down time distributions and availability, local optimization from a focus on batch sizes and trains, imbalanced interruptions of production wafer throughput to handle development lots, and start profiles. This imbalance generates lost production opportunities from starved tools, excessive tardiness of lots due to poor pacing, and a whipsaw affect in output. This method develops and advocates explicit actions in assigning a lot to a tool (what next dispatch decision) to maintain balance or put in place a path to recovered balance while adjusting for short term output needs and intrinsic throughput characteristics of tools.

Incorporation WIP Balance Concerns in the Dispatch Decision

Process engineers, industrial engineers, and operations research professionals have recently observed the productivity of full automated wafer fabrication facilities can be substantively improved if WIP balance or distribution is incorporated into the dispatch decision process. This introduces a new requirement on the decision process to assign or match lots with tools when the tool becomes free. This is called a WIP balance advocate which monitors the WIP distribution on a regular based and sends hints or guidelines to the WNM (WIP Network Manager) to use in its dispatch or assignment decision.

Current identified methodologies for assigning lots to tools fail to capture any of this complexity and the corresponding opportunity to enhance the overall manufacturing performance.

The method described here involves (a) establishment of a WIP balance advocate which monitors the position of WIP in the manufacturing line, (b) establishment of a mechanism and form to send "hints" or guidelines to the WNM. These "hints" are incorporated into its assignment or dispatch decision, (c) establishment of a process and algorithm for the WNM to use this guidance within its decision making process, (d) establishment of an overall architecture to implement each component in an integrated fashion and monitor the WIP balance advocates guidance and the level of WNM compliance.

Due to computation and algorithmic limitations, the WIP balance advocate must run outside of the simple rules that execute when a WNM dispatch action is requested by a tool. This method meets this criteria. Additionally, such a process must appropriately couple the guidance with the set of criteria the WNM accounts for in each decision covering such items as lot priorities, due dates and lo...