Modeling and experimental simulation of the low-frequency transfer inefficiency in bucket-brigade devices

The work presented in this paper extends the available theory and it also presents a model for the low-frequency charge transfer in MOS bucket-brigade devices (BBD's). Our new theory which characterizes the low-frequency component of transfer inefficiency in terms of the subthreshold current is frequency independent and it incorporates both channel-length and barrier-height modulations. This model was verified experimentally on simulated BBD's. After proving both theoretically and experimentally that the low-frequency transfer inefficiency of BBD devices is due to subthreshold current, we successfully used this knowledge to design an improved BBD device. This improved device includes only one extra ion-implantation step relative to the original BBD device. An ion implant is used in part of the BBD channel.     

Transversal filtering using charge-transfer devices

Techniques are presented for making transversal filters using charge-coupled devices and bucket-brigade devices. In a CCD transversal filter, the delayed signals are sampled by measuring the current flowing the clock lines during transfer, and the sampled signals are weighted by a split electrode technique. In a BBD transversal filter, the delayed signals are `tapped' with a source follower whose load determines the weighting coefficient. Examples are given of CCD and BBD filters that are `matched' to particular signalling waveforms, and the limitations of charge-transfer devices in matched filtering applications are discussed. Finally, the application of CTD transversal filters to other signal processing functions is discussed.     

Wire transfer of charge packets using a CCD-BBD structure forcharge-domain signal processing

A structure for the virtual transfer of charge packets across metal wires is described theoretically and is experimentally verified. The structure is a hybrid of charge-coupled device (CCD) and bucket-brigade device (BBD) elements and permits the topological crossing of charge-domain signals in low power signal processing circuits. A test vehicle consisting of 8-, 32-, and 96-stage delay lines of various geometries implemented in a double-poly, double-metal foundry process is used to characterize the wire-transfer operation. Transfer efficiency ranging between 0.998 and 0.999 is obtained for surface n-channel devices with clock cycle times in the range from 40 ns to 0.3 ms. Transfer efficiency as high as 0.9999 is obtained for buried n-channel devices. Good agreement is found between experiment and simulation     

A high-sensitivity solid-state image sensor using a thin-film ZnSe-Zn1-xCdxTe heterojunction photosensor

A high-sensitivity solid-state image sensor in which a charge-transfer device is overlaid by a thin-film photoconductor for the photosensor has been developed. The scanning registers are composed of interline transfer-type bucket-brigade registers (BBD) in the imaging area and charge-coupled registers (CCD) in the horizontal scanning circuit. The special feature of this device is that the thin-film photoconductor of ZnSe-Zn1-xCdxTe heterojunction is directly formed not only on the Si-diode area but also on the scanning circuit area of BBD to obtain a high-aperture ratio. This solid-state image sensor has 506^V× 413^Hpicture elements and the imaging area is about 10.4^V× 13.5^Hmm which corresponds to that of a 1-in vidicon. High sensitivity of 0.46 µA/lx (2856 K) and large blooming control capability have been obtained by this structure. The characteristics such as sensitivity, dark current, resolution, and blooming peculiar to the structure of a solid-state imager overlaid by a photoconductor are also discussed.     

Step and frequency responses of c.t.d.s with nonuniform transfer inefficiency

General models for the small-signal step and frequency responses of charge-transfer devices with nonuniform inefficiency are derived. The case when the transfer inefficiency becomes position-dependent due to a nonuniform distribution of the background charge along the register is experimentally investigated using bucket-brigade delay lines as test vehicles.     

The bipolar transistor bucket-brigade shift register

An analysis of the bipolar transistor bucket-brigade shift-register operation is presented for comparison to other charge-transfer shift-register schemes. It is shown that incomplete charge transfer, the most important performance limiting effect for the charge-coupled device and the IGFET bucket brigade, is very small under most practical operating conditions for the bipolar transistor bucket brigade. In addition to charge loss due to finite transistor current gain h/SUB fe/ the next most important performance limitation comes from collector-emitter capacitance. It is shown that this collector-emitter capacitance leads to reduced analog time delay on transfer through the register and to signal attenuation effects similar to those resulting from incomplete charge transfer. Using the results of the analysis, experimental data reported by Sangster are discussed and a comparison of the advantages and disadvantages of the bipolar bucket-brigade register with the MOS charge-transfer registers is made.     

Bucket-brigade bandwidth characteristics

The range of applications of bucket-brigade circuits is limited by inherent device limitations. At present, the most severe of these appears to be a relatively poor charge-transfer efficiency, which results in a limited signal bandwidth. In this letter, the bandwidth characteristics of bucket-brigade circuits are described, and close agreement between computed and experimental results is shown.     

Digital signal transfer in charge-transfer devices

The nonlinear properties of digital signal transfer through charge-coupled device and bucket-brigade shift registers are considered in terms of adjacent bit charge levels. A signal transfer efficiency is defined and shown to be a useful parameter for charge-transfer device shift register simulation. Approximate equations are developed for the worst case output bit levels and an approximate formula for the optimum input `fat' zero level, with respect to the worst case output signal `window', is obtained. The analysis includes only the intrinsic incomplete charge transfer properties of CTD's under square-wave clock pulsing conditions. Comparison of the theory and preliminary experimental results for CCD indicate good quantitative agreement.     

Charge transfer and blooming suppression of charge transfer photodiode area array

A charge-transfer photodiode array combines the advantages of diffused diodes for broad and smooth spectral response and analog registers for low-noise readout. The device structure described is that of a high-speed low-blooming 100-by-100 diode array using bucket-brigade readout registers. Two of the mechanisms which are essential to successful operation of this combination structure are studied. These mechanisms are the charge transfer from sensing diode to the analog register and blooming suppression. It is found that the charge-transfer speed degrades sharply with reducing light level due to subthreshold leakage behavior of the MOS transfer gate. This degradation is eliminated by using a background charge supplied from the analog register. Experimental data confirms the validity of the concept.     

An experimental TV ghost-suppressor circuit using charge-transfer devices

The rapid development of charge-transfer technology has fostered many new applications of charge-transfer devices (CTD's) in the field of analog-signal processing. In this paper, the realization of a TV ghost-suppressor circuit by means of a pair of 64-stage p-channel MOS bucket-brigade circuits is described and experimental results are reported.     

红外面阵探测器DTDI技术的性能分析

戽链（BBD）结构的CMOS红外模拟TDI探测器,由于其兼容普通CMOS工艺,并可以提高系统的信噪比,因而在空间遥感领域得到了广泛的应用。而基于焦平面面阵的数字TDI（Digital Time Delay and Integration）技术的研究与应用尚在起步阶段。利用中国生产的320256中波面阵红外探测器进行DTDI研究,对比分析了模拟TDI探测器的电子转移效率、BBD噪声、动态范围等方面的性能,突出了DTDI在结构和性能上的优势,并通过理论推导了DTDI对面阵探测器本身信噪比的提高,非均匀性的改善,同时分析了DTDI过程中盲元对性能的影响。最后,通过实验得到了16级DTDI的信噪比增加为2.5倍,非均匀性减少到1.68%,验证了DTDI技术对系统性能的改善,为DTDI技术的应用提供了理论参考。     

Free charge propagation in a resistive-gate MOS transmission line

A detailed computer analysis of the charge-transport process in an MOS transmission line (MOSTL)operating in deep depletion is presented. The mathematical model is developed taking into account time-dependent gate voltages, field-dependent surface mobility, and voltage-dependent depletion capacitance. A distributed transmission line circuit model similar to that obtained in a previous work for charge-transfer devices is derived. The charge-propagation characteristics are discussed and interpreted. The contributions of the physical transport mechanisms are investigated from the standpoint of assessing the influence of the design parameters and operating conditions on the performances of the structure. Several driving techniques which use time-varying gate voltages are proposed and simulated. Special emphasis is directed toward the possible improvements in the performances of an MOSTL used as a bit line in a continuously charge-coupled RAM or as a variable delay line for digital signals. Under some simplifying assumptions, an approximate model which yields closed-form solutions for the operational parameters of interest that compare well with the numerical calculations is developed. To a certain extent, the theory derived in this paper is also valid for charge-transfer devices, in particular for the charge-transfer process in bucket-brigade devices and under the transfer gates of two-phase CCD's.     

Tunable Matched Filters for Pulse-Code Modulation Using Charge-Transfer Devices

A tunable matched filter for the major PCM codes has been synthesized utilizing a developmental bucket-brigade delay (BBD) line. The variable delay feature of the BBD allows continuous tuning of the matched filter over a wide range of bit rates. By combining and weighting the outputs of two BBD lines, matched filters for nonreturn-to-zero (NRZ), return-to-zero (RZ), and biphase codes are realized with a signal-to-noise performance within 0.8 dB of theoretical.     

Moving-target-indicator recursive radar filter using bucket-brigade circuits

A prototype clutter-rejection filter for radar is described. It uses analogue shift registers of the bucket-brigade type, which, in common with charge-coupled devices, can combine the flexibility of digital processing with the simplicity of analogue operation. Certain imperfections in the devices are shown to be particularly important for moving-target-indicator filtering.     

Self-scanned image sensors based on charge transfer by the bucket-brigade method

Solid-state image sensors which are internally scanned by charge transfer offer a potentially usefull alternative to sensors based onx-yaddressing. The application of charge transfer to solid-state scanning introduces sensor design problems which are common to either the "bucket-brigade" or "charge-coupled" approach. Two-dimensional and single-line sensors employing bucket-brigade scanning have been built and evaluated. Problems discussed include transfer efficiency, video signal extraction, vertical scanning, and spurious effects. The use of the bucket-brigade shift register as a scan generator forx-yaddressing is also described.     

A charge-transfer multiplying digital-to-analog converter

A new charge-transfer multiplying digital-to-analog converter employs an array of binary-weighted MOS capacitors and MOS transistors as its only elements. It can be fabricated on the same chip and by the same process as most charge-coupled devices and bucket-brigade devices, and provides two- or four-quadrant multiplication. An experimental n-channel metal-gate MOS realization demonstrated accuracy to 7 bits plus sign, total harmonic distortion 60 dB below fundamental, 70 dB dynamic range, and 200 kHz bandwidth.     

Charge-transfer readout and white-video-defect suppression in X-Y image sensors

A method of detecting photosignals in solid-state image sensors is described. The technique employes bucket-brigade charge-transfer readout of a modified X-Y imaging array. This concept is further developed to cover its use in a single-pellet tricolor image sensor. A natural extension of this same bucket-brigade fan-in circuit leads to a method of mitigating the effects of white video defects in both solid-state image sensors and beam-scanned tubes.     

适用于按比例缩小至亚10nm的圆柱体全包围栅场效应管仿真

提出了一种适用于按比例缩小至亚10nm的圆柱体全包围栅场效应管.报道了圆柱体全包围栅场效应管器件物理分析、技术仿真结果以及器件制作详细工艺流程.与其他常规鳍形场效应管器件(FinFET)相比,该器件特别适用于解决常规鳍形场效应管器件所面临的问题,进一步提高器件性能及按比例缩小能力.技术仿真结果显示,圆柱体全包围栅场效应管具备许多常规鳍形场效应管器件,其中包括长方体全包围栅场效应管所不具备的优点.就圆柱体全包围栅场效应管器件结构而言,该器件由无数多个将圆柱体形沟道全部包围的栅所控制.由于克服了由不对称场的积聚,如锐角效应所导致的漏电,器件沟道的电完整性得到很大改善.详细讨论了器件制作工艺流程,提出的工艺流程简单并且与常规CMOS工艺流程兼容.     

适用于按比例缩小至亚10nm的圆柱体全包围栅场效应管仿真

提出了一种适用于按比例缩小至亚10nm的圆柱体全包围栅场效应管.报道了圆柱体全包围栅场效应管器件物理分析、技术仿真结果以及器件制作详细工艺流程.与其他常规鳍形场效应管器件(FinFET)相比,该器件特别适用于解决常规鳍形场效应管器件所面临的问题,进一步提高器件性能及按比例缩小能力.技术仿真结果显示,圆柱体全包围栅场效应管具备许多常规鳍形场效应管器件,其中包括长方体全包围栅场效应管所不具备的优点.就圆柱体全包围栅场效应管器件结构而言,该器件由无数多个将圆柱体形沟道全部包围的栅所控制.由于克服了由不对称场的积聚,如锐角效应所导致的漏电,器件沟道的电完整性得到很大改善.详细讨论了器件制作工艺流程,提出的工艺流程简单并且与常规CMOS工艺流程兼容.     

Bucket-brigade device with improved charge transfer

The charge transfer of bucket-brigade devices can be considerably improved by the additional use of one transistor and one resistor per cell. The effect of this is demonstrated by a computer simulation.