Semiconductor Tool Offset Modeling for Backup Wafer Processing
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Solution Overview
Problem
In semiconductor device manufacturing, machinery offset times vary significantly from calculated processing times due to imperfections and process variations, leading to inefficiencies and reduced production yield, especially when backup machines are used during preventive maintenance.
Innovation Solution
A method is developed to determine offset times by collecting and analyzing process control parameters, separating the offset into tool and product contributions, and using statistical analysis to stabilize product offsets, thereby reducing the number of test wafers needed and increasing production efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If test wafers are processed and analyzed to determine offset time, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The system performs preliminary characterization of each processing tool to establish its specific offset time before actual production. By pre-determining the offset time for each tool through initial measurements and storing this information in a database, the system eliminates the need to process test wafers during production runs, thereby maintaining measurement precision while preventing productivity loss.
Solution Approach 2:
The system creates a virtual model of each processing tool's performance characteristics including its offset time. Instead of physically processing test wafers to determine offset time, the system uses copied data from previous measurements and database records to simulate and determine the offset time, eliminating the need for actual test wafer processing during production.
2Reliability
If backup machinery is used during preventive maintenance, then reliability is improved, but manufacturing precision deteriorates due to different offset times
Solution Approach 1:
The system adjusts the processing parameters specifically for each backup tool by determining and applying its unique offset time. When a backup tool is activated during preventive maintenance, the system retrieves the backup tool's specific offset time from the database and uses this corrected parameter to compensate for the tool's inherent timing variations, thereby maintaining manufacturing precision across different tools.
Solution Approach 2:
The system implements a feedback mechanism where the actual processing time and offset time of each tool (including backup tools) are measured, stored, and used to adjust future processing schedules. This continuous feedback loop ensures that even when switching between different tools or backup tools, the system adapts to each tool's specific characteristics to maintain consistent processing accuracy.
Data Source
AI summary
A method includes calculating a processing tool offset for a processing tool based on process control parameters, wherein the processing tool offset is a first portion of a process offset time attributable to a processing tool. The method further includes calculating a product offset based on the process control parameters, wherein the product tool offset is a second portion of the process offset time attributable to a product. The method further includes determining whether the product offset is stable based on a difference between a processing time for different products being within a pre-determined tolerance and a number of processed wafers exceeding a threshold amount. The method further includes calculating an offset time for processing the product using the processing tool based on the calculated processing tool offset, without considering the product offset in response to a determination that the product offset is stable.