In this work, we prepared one kind of metallic golden wafer coated with tantalum/tantalum nitride (Ta/TaN) films or single Ta film by either PVD (Physical Vapor Deposition ) process or ALD (Atomic layer deposition) process to alleviate the charge accumulation and mitigate the electrostatic enhanced impurity adsorption. Through this approach, the charging effect on line CD measurement is effectively eliminated. We compared the charging effect among normal wafer, metallic golden wafer, and the evaluated golden wafer’s life time in terms of charging effect prevention by means of a long-term test. Moreover, to extend the lifetime of golden wafer, a rework process was investigated to deoxidize the surface oxidation layer and prevent it from the charging induced long-term performance degradation. For CD-SEM stability control, we designed a daily monitor flow utilizing the golden wafer to ensure and maintain a healthy CDSEM condition for in-line product measurement. Finally, we extended the concept of this metallic golden wafer into other potential metrology related applications such as CD-SEM tool matching and calibration.
At advanced node, mask making details need to be taken into account in OPC in order to achieve the demanded accuracy. Mask corner rounding, which is often emulated by corner chopping of polygons in OPC implementation, is one such an example. In this work, we demonstrated fixed radius corner-chop improves OPC accuracy, however, such an implementation is unable to offer required OPC accuracy, since it still leaves non-negligible ADI error at some random 2D patterns. A 3-segments rule based chop strategy is proposed and tested with which significant simulation accuracy improvement is achieved at little extra computational cost.
In this work, Optical Critical Dimension (OCD) spectroscopy was used to monitor the critical dimension for After-Etch Inspection (AEI) structures at sub 65 nm node, such as Poly Gate, Shallow Trench Isolation, Offset Spacer, and Oxide-Nitride Spacer. The dynamic repeatability of the measurement was obtained through a 10-cycle measurement process with loading and unloading wafers. The long-term stability was examined with more than 3 day's measurements. The good correlation results between the OCD spectroscopic tool and reference tools, such as, CD Scanning Electron Microscope and Transmission Electron Microscopy, were obtained. The results demonstrated that the OCD spectroscopic tool has advantages of high precision and high stability for 65 nm node and beyond.
There exist great difficulties and challenges in CD-SEM matching because of the destructive interaction between e-beam and resist. This paper presents a new cross sampling method which uses two separate locations of resist line and performs cross measurements by two separate tools in a special sequence. This sampling method together with a special designed calculation can eliminate the impact from both resist line shrinkage and measurement locations difference. It removes the error component with magnitude of second shrinkage in the conventional approach of matching, however a difference of second shrinkages from two tools is introduced although it is smaller than the second shrinkage itself. After introduce an exponential decay model of the resist shrinkages in multiple subsequent measurements to the sampling method, we could estimate first and second shrinkages for both CD-SEM tools with the measurement results from one of the above cross sampling plan, we are able to determine the real difference of measured CDs after the first measurement from these two CD-SEM tools, which cannot be obtained by direct measurements because of the memory of any previous measurement. IntroductionMatching evaluation between metrology tools in IC manufacturing is needed for accurate and consistent measurement of process. Critical dimension-scanning electron microscope (CD-SEM) has an important role in measuring critical dimension of pattern on wafer. The accuracy of measurement for critical dimension has large influence on process, so the CD-SEMs must be matched with each other within specified requirements.After etch inspection (AEI) wafer is commonly used in CD-SEM matching, because AEI wafer has high contrast, and no destructive puzzle such as shrinkage on after development inspection (ADI) wafer after exposure by e-beam. It is convenient to do match using AEI wafer. But some report [1][2] [3] shows that it is necessary to do matching for CD-SEM by ADI wafer. There are two main reasons: first, AEI wafer has higher contrast and resolution than ADI wafer when they are measured by CD-SEM, these advantage brings coarse matching result which could not reflect the inherent difference about the two CD-SEMs. Second, the shrinkage for photo resist on ADI wafer is sensitive to both time and intensity of e-beam while AEI wafer is not, matching on ADI wafer will reflect more sensitively whether two CD-SEMs are matched or not. Further more, in some conditions, matching between two CD-SEMs for ADI critical dimension (CD) has to be used for matching purpose, for example, when the ADI CD measurement for a BEOL process is transferred from one FEOL CD-SEM to another, AEI wafer could not be used because of Cu contamination.Shrinkage is an inherent shortcoming for ADI wafer to do matching between two CDSEMs, the measure on ADI wafer is destructive, so the true value of the CD on ADI
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