| dc.description.abstract | As demand of memory capacity for increase in electronic devices, demand of highly-dense memory, low-power, and highly-secured chips also increases. One-Time Programming (OTP) memory becomes more and more important. To prevent stored data from being hacked, a secure -key storage is necessity. In comparison with the Mask ROM, One-Time Programming (OTP) memory has more flexibility. It can make code changes after the chip has been manufactured, effectively reducing time for debugging and updating. Hence, the operation speed is faster. It also eliminates the need to duplication of codes for on-chip random access memory (RAM), which reduces startup time. To support this functionality, a charge storage operating mechanism is used by users to program the OTP cell. In comparison with the anti-fuse (OTP) and electronic fuse (efuse OTP), our single-transistor charged-based one-time Programming (OTP) memory has the advantages of lower operating voltage, smaller area, and lower power consumption.
The OTP MACRO is divided into four parts: decoder, memory array, sense amplifier and logic control circuit. The decoder selects an address in the array under different operating conditions. It also applies the operating voltages to ensure that the unselected cells area not affect by the operation voltage under the selected one. The sense amplifier uses the current sensing mode for readout the information stored in the 1T OTP cell, which can read a small current amount with a large sensing margin so as to read more accurately.
This work designs an OTP memory array with the capacity of 4-k cells, which shows advantages of fast operation speed (1s) and low programming voltage (1.8V) in programming. Another benefit of this OTP memory array is smaller cell-size. The unit area is only 0.1452μm2 per cell. Furthermore, to increase memory capacity aggressively, 3-bits-per-cell storage is achieved through different incremental programming voltages. This array also achieves a low bit error rate of 1.76% when random-access is performed. As a result, reliabilities are also evaluated, the memory array can keep information after baked in 740 hours at 125 Celsius.
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