Semiconductor Pad Logic Fixing for Wafer Burn-In Reset Stability
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Solution Overview
Problem
Semiconductor devices face issues during wafer burn-in tests due to incorrectly inputted electric signals to unused pads, leading to inaccurate test results and potential misclassification of normal devices as defective, and the internal circuits may be improperly initialized due to external reset signals with incorrect logic levels.
Innovation Solution
A semiconductor device design that includes a signal generating unit for test mode selection, a reset unit for initializing internal circuits, and a logic level fixing unit to output a fixed signal regardless of external signal logic levels, ensuring proper operation during wafer burn-in tests by filtering out incorrect reset signals and maintaining internal circuit stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an exclusive pad for receiving external reset signal is added to the semiconductor device, then the reliability of reset signal activation is improved, but the device complexity increases due to additional pads and signal routing
Solution Approach 1:
The patent makes existing pads multi-functional by enabling them to serve both as general-purpose I/O pads during normal operation and as reset signal reception pads during wafer burn-in tests. The mode register set (MRS) controls the functionality of pads dynamically, allowing the same pad structure to fulfill multiple purposes without adding exclusive reset pads, thereby improving reset reliability while avoiding increased device complexity.
2Ease of operation
If all pads are made responsive to external signals during wafer burn-in test, then the ease of operation is improved, but the measurement precision deteriorates due to noise coupling from adjacent pads
Solution Approach 1:
The patent applies local quality by selectively controlling the electrical state of individual pads based on their usage status during wafer burn-in tests. Used pads are configured to receive external signals with proper impedance matching, while unused pads are placed in high-impedance floating state to prevent noise coupling. This localized differentiation allows easy operation on used pads while maintaining measurement precision by isolating unused pads from signal interference.
Solution Approach 2:
The patent dynamically changes the electrical characteristics of pads based on real-time test conditions. The mode register set (MRS) enables dynamic reconfiguration of pad functionality during wafer burn-in tests, allowing the system to switch between signal reception mode and high-impedance floating mode for different pads. This dynamic adaptation ensures that pads are only responsive when needed, preventing noise coupling while maintaining operational ease for active test signals.
3Manufacturing precision
If unused pads are left floating during wafer burn-in test, then the manufacturing precision is improved by preventing noise interference, but the reliability deteriorates when external reset signals are mistakenly input to these pads
Solution Approach 1:
The patent introduces the mode register set (MRS) as an intermediary control mechanism that mediates between the external signal environment and the internal circuitry. The MRS monitors test mode activation and uses this information to control the electrical state of pads through buffer circuits. When test mode is active, the MRS configures unused pads to high-impedance state to prevent noise interference, while simultaneously enabling used pads to properly receive external signals including reset signals, thus resolving the reliability concern about mistaken reset signal input.
Solution Approach 2:
The patent changes the electrical parameters (impedance, signal reception state) of pads based on the operational mode. During wafer burn-in tests, the mode register set (MRS) triggers parameter changes that transform unused pads from signal-receiving state to high-impedance floating state to prevent noise interference. Simultaneously, used pads maintain or transition to signal-receiving state, allowing proper reception of external reset signals. This parameter-based control resolves the contradiction by making pad behavior adaptive to test conditions.
Data Source
AI summary
A semiconductor device includes a plurality of pads configured to receive a plurality of external signals, an internal circuit configured to perform a predetermined internal operation in response to one of the external signals that is inputted through one of the plurality of pads, and a signal transferring unit configured to receive the external signal, output the external signal to an internal circuit an output signal during a normal mode, and output a fixed signal regardless of changes in the external signal to the internal circuit in a test mode.