Circuit and method to measure threshold voltage distributions in SRAM devices
US7352252B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 11, 2006 |
| Grant date | Apr 1, 2008 |
| Priority date | — |
| Expiry date | Oct 19, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2029/0403
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A circuit for inline testing of memory devices which provides information on the variation of the threshold voltage. The circuit includes an array of ring oscillators with a series of inverters, which already exist in the memory device. A control logic systematically steps through all of the ring oscillators by enabling each inverter and toggling the input. The mean frequency and its distribution is measured and recorded in an output circuit. The threshold voltage variation in the memory device is deduced from the ring oscillators. The circuit additionally includes two inverters place external of the memory device. Each ring oscillator is coupled to an inverter. The inverter preconditions the elements of the ring oscillator to prevent a resistive divider between the two transistors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.