Design And Implementation Of Rapid Test System On WAT

Under the guidance of Moore's Law,the integrated circuit(IC)process has been evolving forward from micrometer-scale to nanometer-scale;particularly in recent years,the scaling speed even accelerates more than before.Therefore,any small deviation in each manufacturing process step will now affect the yield of chips,especially at advanced process nodes(below 14 nm).In order to improve the product yield,a large number of test structures must be added to monitor each manufacturing process,which leads to the rapid growth of test items;hence the requirements for the test speed of test equipment are getting higher and higher.However,the test speed of Wafer Acceptance Test(WAT)equipments on the market today cannot meet well the requirements of the rapid development of IC scaling.To solve the problem that the test equipments cannot meet the test speed requirements,a rapid WAT test system has been studied and designed in this thesis,particularly its test speed has been improved through the following innovations:1.According to the characteristics of WAT test,the test process has been optimized to reduce the time consumed by the frequent startups of the test hardware,so that the test speed is increased by about 20%,and in some special applications it can reach 88%.Besides,the automated test technology(GEM)is introduced to minimize the time consumed by manual interventions during the test procedures.2.By taking advantage of high-speed source measurement units(SMU)and data transmission technology,test data transmission rate and the sampling rate of measurement modules are both increased in this system.The sampling rate reaches up to 1.8 MS/s,which is more than 3 times of the rate for traditional system.The data transmission speed is improved from 1.4 MB/s(traditional speed)to 500 MB/s;therefore,it become negligible during such rapid testing.3.Parallel test method which allows test modules to work parallel,and multi-pins probe card technology are both introduced into the rapid test system.Under the condition of satisfying high accuracy,the test speed has been improved by 20?25times compared to traditional sequential test.In order to achieve the maximum number(25)of parallel tests,a 4-channel probe card is designed to reduce the prober moving time to a quarter of the original.In this thesis,a rapid WAT test system prototype has been designed and implemented.Overall,while ensuring the requirements of high accuracy,the test speed can be increased by 2 to 5 times;in some special applications the acceleration can even reach to more than 10 times.