Semiconductor Output Pad Switching Circuit for Probe Testing
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Solution Overview
Problem
Semiconductor devices with a large number of output terminals face challenges in testing due to the need for narrow spacing between pads, which complicates probe needle contact and requires additional test pads, leading to increased device size and potential degradation in output characteristics.
Innovation Solution
A semiconductor device with a signal processing circuit, output pads, and a switch configuration that allows for testing without dedicated test pads by using a shorting pad and switches to connect or disconnect the signal processing circuit from the output pad, enabling testing through existing output pads without passing through a switch element during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the space between adjacent pads is narrowed to accommodate a large number of output terminals, then the IC chip area is reduced, but it becomes difficult for probe needles to contact each pad without interference
Solution Approach 1:
The patent merges multiple output signals into a single test pad by using a switching circuit that sequentially connects different output terminals to the same pad. This allows probe needles to contact only one pad while still testing multiple output terminals, solving the problem of narrow pad spacing making probe contact difficult.
Solution Approach 2:
The test pad is given multiple functions: it serves as both a normal output pad and a testing point for multiple other output terminals. The switching circuit enables the test pad to be universally connected to different output terminals during testing, eliminating the need for separate dedicated test pads for each output terminal.
2Ease of operation
If dedicated test pads are added for testing, then probe needle contact is facilitated, but the area available for primary function circuitry is proportionally reduced
Solution Approach 1:
The patent makes one of the existing output pads serve as a test pad for multiple other output terminals through the switching circuit. This multi-functional approach eliminates the need for additional dedicated test pads, preserving chip area for primary function circuitry while still enabling easy probe needle contact during testing.
Solution Approach 2:
The system uses its own existing output pads and switching circuitry to perform testing functions, rather than requiring separate dedicated test infrastructure. The output buffer and switching circuit work together to enable self-testing through the existing pad structure.
3Ease of operation
If a switch element is used to disconnect the output buffer from the output pad during testing, then testing can be performed, but a transistor with low on resistance is required, increasing the device size
Solution Approach 1:
The patent extracts the switching function from the critical signal path during normal operation. The switching circuit is configured to operate only during testing mode, disconnecting from the normal output path. This allows the use of larger switch elements optimized for testing without affecting normal device performance or increasing the size of the critical signal path components.
Solution Approach 2:
The switching circuit dynamically changes its state based on operating mode (normal vs. testing). During normal operation, the switch is disconnected from the output path; during testing, it connects the test pad to the output buffer. This dynamic behavior allows the switch element to be optimized for testing requirements without permanently impacting the device size or performance.
Data Source
AI summary
A semiconductor device includes a signal processing circuit configured to generate an output signal, an output pad, an output line connecting the signal processing circuit to the output pad, the output signal from the signal processing circuit being output from the output pad through the output line, a shorting pad formed in the output line, a switch connected between the shorting pad and the output pad, and configured to connect the signal processing circuit to the output pad when the switch is on, and disconnect the signal processing circuit from the output pad when the switch is off, and a wiring line connecting the shorting pad to the output pad.