Semiconductor Tool Offset Control for Stable Wafer Processing
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Solution Overview
Problem
Machinery used in semiconductor device manufacturing experiences offset 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, including processing times and product types, to calculate tool and product offsets, allowing for adjustments to reduce accumulated error and improve yield.
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 behavior before actual production. By pre-determining tool-specific offset characteristics through initial measurements and storing them in a database, the system eliminates the need for continuous test wafer processing during production, thereby maintaining measurement precision while preserving productivity.
Solution Approach 2:
Instead of continuously processing physical test wafers to determine offset times, the system creates and uses a digital model (copy) of each tool's offset behavior. The offset time database stores characterized parameters that replicate the tool's performance characteristics, allowing offset determination without repeated physical testing, thus resolving the contradiction between measurement accuracy and production efficiency.
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 compensates for differences in offset times between primary and backup machinery by adjusting process parameters. When switching to backup equipment, the control system retrieves the backup tool's specific offset characteristics from the database and modifies processing times accordingly, maintaining manufacturing precision across different machines while ensuring continuous production through preventive maintenance.
Solution Approach 2:
The system implements feedback control by continuously monitoring actual processing outcomes and comparing them against expected results based on tool-specific offset parameters. When using backup machinery, the system adjusts processing parameters in real-time based on feedback from the offset time database, ensuring that precision is maintained despite switching between different equipment during preventive maintenance cycles.
Data Source
AI summary
A method includes calculating a processing tool offset for a processing tool, 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, 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 pre-determined tolerance and a number of processed wafers. 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.