Bi-directional Software Watchdog for Semiconductor Controller Safety

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Solution Overview

Problem

In semiconductor manufacturing, conventional controllers like personal computers can fail unpredictably, leading to undetected anomalies and potential hazards due to the lack of effective monitoring of their states, particularly in software malfunctions which can result in uncontrolled device operations, posing risks to equipment and personnel safety.

Innovation Solution

A bi-directional software Watch Dog Timer (WDT) system is implemented, where a first program on the module controller and a second program on the device interaction unit exchange counter values to monitor each other's execution states, determining anomalies and initiating safe termination of operations if abnormalities are detected, without requiring additional hardware modifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional personal computers are used as controllers, then cost is reduced, but reliability deteriorates due to component lifespan limitations and unpredictable failures

Engineering Contradiction:

Improvecontroller costVSAvoidcontroller reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent implements a watchdog timer mechanism that continuously monitors controller operation and provides feedback. When the controller fails to update the watchdog timer within a predetermined period, the system detects the failure and terminates the controller program, preventing unsafe continuous operation of controlled devices

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The watchdog timer is configured to terminate the controller program before hazardous conditions can develop. By monitoring elapsed time and automatically stopping the controller when the predetermined period expires without updates, the system prevents potential damage to equipment and personnel

Inventive Principle:

Principle #10Preliminary action

2Reliability

If hardware watchdog timer circuits are added to monitor controller execution, then reliability improves, but device complexity increases

Engineering Contradiction:

Improvecontroller monitoring capabilityVSAvoidhardware structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces hardware watchdog timer circuits with a software-based implementation. The monitoring function is achieved through program logic that tracks elapsed time using software counters and conditional statements, eliminating the need for additional hardware components while maintaining the reliability benefits of watchdog monitoring

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Difficulty of detecting and measuring

If unidirectional monitoring from controller to device is implemented, then monitoring capability improves, but safety deteriorates when interface boards fail

Engineering Contradiction:

Improveexecution state monitoringVSAvoidunsafe operation from interface board failure

Core Design Contradiction:

Difficulty of detecting and measuringVSObject-affected harmful factors

Solution Approach 1:

The patent implements bidirectional monitoring where not only does the controller monitor the device interaction unit, but the device interaction unit also monitors the controller. This mutual monitoring ensures that failures in either direction are detected, preventing unsafe conditions from developing regardless of which component fails

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS7945345B2Semiconductor manufacturing apparatus

Publication Date: 2011.05.17 ASM JAPAN

AI summary

A semiconductor manufacturing apparatus includes a first program on a controller and a second program on an interface board between the controller and controlled devices. Both of the programs update their own counters and exchange their counter values with each other, serving as bi-directional software watchdog timers (WDT). If a counter value of the first program on the controller sent to the second program on the interface board is determined to be abnormal by the second program, the second program on the interface board sends commands to the controlled devices to terminate output so that the apparatus is navigated to a safe mode. The first program similarly monitors the counter values of the second program for anomalies. This bi-directional software WDT can be implemented as add-on to software programs that already exist in the controller and the interface board, therefore, this implementation does not incur extra cost of hardware of the apparatus.