Research On Age Sensor Technology Based On TDDB Effect

With the improvement of integrated circuit manufacturing technology,the size of the device in ICs is rapidly reduced,the power supply voltage continuously decrease,and the circuit integration is greatly improved,which makes the aging problem becomes increasingly serious.When the feature size of the integrated circuit is less than 90 nm,the electric field intensity in the gate oxide layer increases rapidly,while the Time Dependent Dielectric Breakdown(TDDB)has become the main reason for the aging of the integrated circuit chip.While the integrated circuit industry is in replacement quickly,the chips with bad performance caused by aging will be eliminated eventually,but the recycled chips are not destroyed after the destruction and re-enter the market.According to reports,the number of counterfeit IC chips in the market is rising continuously and even increasing exponentially.These counterfeit chips are difficult to detect,because the current detection technology is not perfect yet,and not suitable for users to use.In this paper,we hope to develop an on-chip sensor technology which can detect the chip's age.By using the age sensor,users can differentiate between the recycled IC and fresh IC.In this paper,the TDDB breakdown of the MOS capacitor is monitored by the sensing circuit,then the life model is used to calculate the use of age.The following research work is carried out for the gate oxide TDDB effect and the integrated circuit age sensor:1.The breakdown mechanism of the gate oxide layer and several major TDDB models are analyzed in detail.The accelerated experiments with different temperature and voltage stress were carried out respectively on the NMOSFETs to test their corresponding breakdown times,which is in the TSMC 0.18?m process by using the constant voltage method.The gate oxide thickness of NMOSFETs is 3.56 nm and the ratio of width to length is 0.22 / 0.18.According to the breakdown time of the samples under different stress,the cumulative failure distribution and the characteristic life of the gate oxide layer are obtained,and the extraction and verification of the V model parameters are completed.2.By studying the related concepts and research results of age sensors,a new type of age sensor structure based on redundant redundant warning element is proposed by using the TDDB effect of circuit aging.The age sensor comprises a stress voltage generating circuit,a device under test(DUT)circuit and a micro-current conversion circuit.Compared with the conventional age sensors,the sensor proposed in this paper does not need to set the reference circuit.It can use the TDDB aging characteristics of the NMOSFET to calculate the using time of ICs by monitoring the DUT's TDDB effect,which can eliminate the inaccuracy of the reference circuit,thus the life calculation has a higher accuracy.3.Design each module circuit of the sensor structure,and Cadence Virtuoso simulation tools is uesd to simulate the circuit.The result shows that the output signal of the sensor is low before the TDDB breakdown happens on the NMOSFETs,which are in the DUT circuit.At the moment of TDDB breakdown,the circuit monitors the change of the current,and the output signal goes high,and the functional requirements of the circuit module are realized.