Two-dimensional transient analysis of buried-channel charge-coupled devices
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Since the invention of charge-coupled device (CCD) by W. S. Boyle and G. E. Smith in 1970, this device has drawn tremendous attention. CCD is considered as an important milestone in the electronic industry;In 1972, a new structure of CCD, called buried-channel charge-coupled device (BCCD) was proposed and it brought significant improvement of the transfer efficiency. In BCCD, the transfer process is basically two-dimensional and thus a two-dimensional analysis of the charge transport is highly desirable. This kind of analysis can provide information for optimum designs and prediction of device performance. However, so far this kind of study has not been done accurately because of the prohibiting length of computer time required;With a new approach, an accurate two-dimensional transient analysis of BCCD has been done. The Finite Fourier Transform method is used to solve the Poisson equation and results obtained by this method are in excellent agreement with those obtained by numerical iteration method such as overrelaxation method. The Finite Fourier Transfer method is about 10 times faster than numerical iteration method. The major advantage of the former method is that one can choose to calculate the potential in the region required, while in numerical method, the potential at all the mesh points has to be calculated;This method of analysis is used to study the effects of different physical and electrical parameters on the performance of a 3-phase BCCD. The results indicate a finite overlap of the clocking pulses is necessary to prevent backward spilling of charge. Operation with trapezoidal clock pulses with long rising time tends to have faster transfer speed than operation using square clock pulses. Higher temperature inside the device can reduce the transfer speed significantly so that it has to be considered in design and applications;With slight modification, this analysis is used to estimate the charge handling capacity. The results show that one-dimensional estimation of the charge handling capacity could be misleading;Using the Finite Fourier Transform method, an accurate analysis of the charge transport process inside a BCCD becomes feasible and the information obtained from this study will be useful in optimization of design.