Impact of body biasing on the retention time of gain-cell memories

Abstract

Gain-cell-based embedded dynamic random-access memory (DRAMs) are a potential high-density alternative to mainstream static random-access memory (SRAM). However, the limited data retention time of these dynamic bitcells results in the need for power-consuming periodic refresh cycles. This Letter measures the impact of body biasing as a control factor to improve the retention time of a 2 kb memory block, and also examines the distribution of the retention time across the entire gain-cell array. The concept is demonstrated through silicon measurements of a test chip manufactured in a logic-compatible 0.18 μm CMOS process. Although there is a large retention time spread across the measured 2 kb gain-cell array, the minimum, average and maximum retention times are all improved by up to two orders of magnitude when sweeping the body voltage over a range of 375 mV.

Keywords

• CMOS integrated circuits
• DRAM chips
• embedded systems
• gain cell-based embedded DRAMs
• SRAM
• limited data retention time
• periodic refresh cycles
• body biasing impact
• memory block
• gain cell array
• silicon measurements
• test chip
• size 0.18 mum
• storage capacity 2 Kbit