Semiconductor Waiting Time Prediction Using Operation-Level ML Models

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Solution Overview

Problem

Current methods for predicting waiting times in semiconductor manufacturing are either inaccurate, resource-intensive, or slow, particularly when using mean cycle times or discrete-event simulations, which are cumbersome and time-consuming to maintain and execute.

Innovation Solution

A method utilizing a machine learning system that predicts waiting times by sampling feature values from a database and training multiple machine learning models for each production operation, allowing for faster execution and easier maintenance, without requiring detailed modeling of interdependencies, and focusing on current production data for more accurate cycle time predictions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If discrete-event simulation is used for waiting time prediction, then prediction accuracy is improved, but execution time and maintenance complexity increase significantly

Engineering Contradiction:
Improveprediction accuracyVSAvoidexecution time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the complex discrete-event simulation into multiple independent machine learning models, each trained on historical data for specific operations or time periods. This segmentation allows parallel execution of multiple simpler models instead of running one complex simulation, significantly reducing execution time while maintaining prediction accuracy through ensemble methods.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent creates simplified copies of the production system using historical data to train machine learning models. These models are lightweight copies that capture essential patterns without the computational overhead of full discrete-event simulations, enabling fast predictions while preserving accuracy through proper training on comprehensive historical datasets.

Inventive Principle:
Principle #26Copying

2Measurement precision

If discrete-event simulation is used for waiting time prediction, then prediction accuracy is improved, but system complexity and maintenance difficulty increase

Engineering Contradiction:
Improveprediction accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical discrete-event simulation system with machine learning models that use statistical patterns from historical data. This substitution eliminates the need to maintain complex simulation logic, event queues, and interdependency models, while preserving prediction capabilities through data-driven approaches that are easier to train and maintain.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses lightweight machine learning models that can be quickly trained and discarded rather than maintaining a single complex simulation system. These models require minimal computational resources and can be retrained efficiently when production patterns change, reducing long-term maintenance complexity compared to discrete-event simulations.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Productivity

If mean cycle time is used for waiting time prediction, then calculation speed is improved, but prediction accuracy deteriorates

Engineering Contradiction:
Improvecalculation speedVSAvoidprediction accuracy
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent transforms the single parameter mean cycle time into multiple parameters including operation-specific waiting times, historical pattern features, and contextual variables. This parameter expansion allows the model to capture variability and patterns that simple means miss, improving accuracy while maintaining fast calculation through efficient feature engineering and model inference.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4231105A1Method for waiting time prediction in semiconductor factory
Publication Date: 2023.08.23 ROBERT BOSCH GMBH

AI summary

A computer-implemented method of waiting time prediction (30) for a route comprising a plurality of production operations in manufacturing, comprising the steps of: Receiving (S31) a sorted list of production operations, wherein the list characterizes the rout for manufacturing a lot; Determining for each production operation in the sorted list: Sampling (S32) feature values for a plurality of features by sampling from a database (51) of collected feature values for the operation measured feature values depending on the starting time point; Predicting (S33) expected waiting time depending on sampled feature values;