The Study Of Four-Probe Measurement System Combining With Image Analysis

Four-point probe measurement technique is one of the most extensive means for examining the resistivity in the semiconductor industry.With continuous progress, semiconductor industry develops at a very fast speed,the integration level of IC becomes higher and higher.Presently,the IC production is entering into the age of ULSI, then testings are more and more important. Many important properties of semiconductor devices are relevant with their resistivity,which brings forward strict demands to the uniformity of the resistivity.Especially micro-area's characteristics attract extensive attention.Under this background, four-point probe measurement technique requires a new development.At present,the problem in testing sheet resistance for micro-areas is that probes must be set up at the suitable locations by handwork.In order to know the wafer's impurity distributing,we need test many times,so will waste a lot of time.If the wafer's diameter would be 300mm,this problem will be more serious.In this paper,image analysis is introduced,through pre-processing and edge picking-up,the probe tips are recognized.Then probe tips will be aligned respectively in two perpendicular directions through driving stepper motors.Thus the distribution of sheet resistance for whole wafer is got by automatic testing and it offers information for detecting the impurity distribution and the diffusion uniformity.In this paper,the circuit used for testing sheet resistance is designed using single chip processor.Additionally,we have expressed Van der pauw function as a polynomial form through local and global reversal development by using the normalized polynomial match,being convenient not only for programming, but also for sheet resistance testing when using Van der pauw and Rymaszewski methods.