Memory Circuit Performance Screening via Ring Oscillator Conversion
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Solution Overview
Problem
Conventional performance screen ring oscillators (PSROs) fail to effectively track the performance of digital integrated circuits, particularly memory devices, leading to significant yield loss due to overly-conservative timing models and growing discrepancies as memory array sizes increase.
Innovation Solution
A semiconductor chip with a digital integrated circuit that can be selectively operated in either a functional mode or a performance screening mode, utilizing a built-in self-test (BIST) engine and a controller to convert the circuit into a PSRO, allowing for internal signal generation and oscillation frequency monitoring to determine performance criteria compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PSRO structures are used for performance screening, then the screening process is simple and does not require complex logic structures, but the PSRO does not effectively track digital integrated circuit performance particularly memory performance leading to significant yield loss
Solution Approach 1:
The memory device is designed to perform multiple functions: normal memory operations and performance screening operations. The same memory cells, wordlines, and bitlines used for data storage are also utilized for performance measurement by converting the memory device into a PSRO structure, eliminating the need for separate dedicated PSRO circuits and achieving both functionality and measurement capability within a single integrated structure.
Solution Approach 2:
The patent introduces a controller as an intermediary component that manages the dual functionality of the memory device. The controller receives external signals, generates internal signals, and coordinates the switching between normal memory operation mode and performance screening mode, enabling the memory device to effectively track performance while maintaining its primary memory function.
2Productivity
If conventional PSROs are used, then the timing models are conservative and simple to implement, but they result in significant yield loss due to overly-conservative timing models and growing discrepancies as memory array sizes increase
Solution Approach 1:
The memory device performs self-testing and self-measurement by converting itself into a PSRO structure. The memory device's own internal signals are used to drive the performance screening process, allowing it to measure its own performance characteristics accurately without relying on external test equipment or conservative timing models, thereby improving both measurement precision and yield.
Solution Approach 2:
The patent changes the operational parameters of the memory device by switching between different modes: normal memory operation mode and performance screening mode. In performance screening mode, the device operates as a ring oscillator with specific signal propagation patterns that allow accurate timing measurement, enabling precise performance characterization that directly improves yield by reducing overly-conservative rejection of functional devices.
Data Source
AI summary
Disclosed is a semiconductor chip with a digital integrated circuit, such as a memory device (e.g., static random access memory (SRAM) arrays, dynamic random access memory (DRAM) arrays, content addressable memory (CAM) arrays, etc), that can be selectively operated in either a functional mode or in a performance screening mode. In the functional mode, a first signal supplied by an external signal generator is used to activate a first device in the circuit and, in response, a second device in the circuit outputs a data output signal. In the performance screening mode, a second signal is internally generated by an internal signal generator based on the data output signal. This second signal is then used to activate the first device in the circuit and, in response, the second device outputs the data output signal. Thus, in the performance screening mode, the digital integrated circuit is effectively converted into a performance screen ring oscillator (PSRO), the output of which can be monitored to determine whether performance criteria for the digital integrated circuit are met.