On-chip Measurement And Application Of Process Variation For Integrated Circuits

With the advances in semiconductor technology,feature size of process continues to shrink.The improvement of integration makes IC design and manufacturing more complex.When the feature size of device is reduced to nano-scale,the process variations have significant impact on performance of device.The process variations may seriously hampered the performance,power and yield of chips.Measurement of process variation which depends on the parameter measurement becomes a research focus in the field of semiconductor technology.By extracting on-chip parameters,we can analyze the distribution of process variations,establish the device models,improve the process and reduce process variation as much as possible.Application of process variation is the development of practical technology based on measurement of process variation.Randomness of process variation may bring unpredictable consequences to the chip,but it shows a high applicability in the field of information security.Process variation is the inevitable product of the manufacturing,and its randomness comes from the intrinsic uncontrollable factors during manufacturing process.By extracting the relevant parameters of the process variation,it can form unique characteristic parameters for each chip and provide an effective solution for the identification of intelligent terminals which is growing popularity.The paper is focused on measurement and application of process variation.Next is a summary of our research contents and innovations:1.A new method of on-chip capacitance array measurement is proposed for the large-scale and high-precision measurement of capacitance parameters on chips.Capacitance parameter is an important basis for evaluating process variations.The extraction of capacitance is helpful for the circuit analysis of delay and reliability.The evaluation of process variations has high demands on the sampling numbers and the accuracy of measurement.On-chip capacitance array measurement system adopts a hierarchical architecture which is flexible and easy to spread,and utilizes capacitance array measurement units as well as analog multiplexers to achieve the measurement target with low area overhead.The capacitance array measurement unit uses the method of charge-based capacitance measurement.We tape out the prototype chips of on-chip capacitance array measurement system in 180 nm CMOS process.The results show the capacitance measurement accuracy reaches 1fF.The distribution of capacitance variation is also shown in the paper,and the factors that may affect the measurement are discussed.2.A new method of on-chip high-resolution timing measurement is proposed.Timing parameters such as rising time,falling time and transmission delay are important for characterization of process.On-chip high-resolution timing measurement system adopts an innovative structure which combines equivalent-time sampling and real-time sampling.Time amplifier is the main achievement of the equivalent-time sampling,which can amplify the measured signals in time domain.The amplified waveforms are oversampled,filtered and converted into digital values for subsequent analysis.We tape out the prototype chips of on-chip high-resolution timing measurement system in 180 nm CMOS process.The high-resolution edge waveforms are measured and the distribution of edge time variation is obtained.The distribution of setup time and hold time are measured for the first time by the method.3.A new concept of physical unclonable hash function(PUHF)is proposed.PUHF can generate an infinite number of challenge-response pairs(CRP)with limited resources.PUHF is a hash function based on the hardware implementation,which use the randomness of process variation to achieve mapping.Referring to the operation of cryptographic hash function,PUHF can generate fixed-length responses by random-length challenges.We tape out the prototype chips of PUHF in 180 nm CMOS process.We evaluate the properties of PUHF on uniqueness,reliability and collision resistant by the measurement results.PUHF cannot be physically copied and is difficult to break reversely.PUHF shows a strong competitiveness in the field of information security.