【作者】 胡滨；

【导师】 李平；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2011， 博士

【摘要】 与制冷红外成像系统相比,非制冷红外成像系统可在室温工作,省掉了昂贵且笨重的制冷设备,从而大大减小了系统的体积、成本和功耗;此外,还可提供更宽的频谱响应和更长的工作时间。国外研制机构已经为军事用户提供了大量成本更低、可靠性更高的高灵敏非制冷红外成像仪。但我国的非制冷红外成像研究与生产起步较晚,且受到工业基础制约,技术远滞后于国外,而市场需求却日益增加,因此发展非制冷红外成像技术已刻不容缓。本文基于以上背景,针对非制冷红外成像系统的核心器件——CMOS焦平面读出电路(ROIC)展开了设计与实现研究。首先在充分了解国内外最新研究动态后,作者作为主研参与了国家973 XXX项目(编号:51313XXX),自主设计并流片验证了单片式320×240非制冷热释电红外焦平面阵列(IRFPA)读出电路,特别是自主设计并验证了单片式耐高温非制冷红外CMOS读出电路的工艺流程,解决了铁电探测材料高温退火与CMOS工艺不兼容的问题。之后作者作为主研又研制了另外两款具有广阔市场前景的红外CMOS焦平面读出电路,即非制冷微测辐射热计160×120读出电路,以及非制冷短波红外320×256多功能快照式读出电路。在以上课题研究中,针对不同类型的非制冷红外探测器,自主设计了相适应的读出电路结构,并全面考虑版图、工艺以及对探测器的接口等问题。本文主要的贡献和创新点如下:1、在铁电型非制冷红外读出电路研制中,提出了一种与标准CMOS工艺兼容的耐熔金属硅化物连线结构,并通过320×240大阵列读出电路的设计、流片及测试验证,获得了有良好耐高温特性的低阻互连线结构,解决了铁电型IRFPA的单片集成耐高温问题。经查新验证,此方法国内外未见报道,已申请中国发明专利并获授权,专利号:200610021450.4。2、针对热释电探测单元是阻抗极高的容性元件,提出了一种基于有源电阻的电阻反馈跨导放大型(RTIA)红外焦平面读出电路结构,该设计采用亚阈区MOS管实现1011Ω以上的有源大电阻,能与热释电红外探测器的阻抗良好匹配,结合两管共源放大器对热释电微弱信号进行高增益电流放大。相对于采用特殊高阻材料的RTIA,本电路不附加材料和工艺,且所采用的三管前置读出结构适用于大阵列热释电焦平面探测器。3、基于前述第2点提到的RTIA,提出采用浅耗尽管(Native MOSFET)作为有源大反馈电阻实现RTIA,因为Native MOS在工艺流程中不增加掩膜版,而且相比工作在亚阈区的增强型MOS,Native MOS的栅极直接接地,省去了偏置电路,且增强了电阻稳定性。4、在非制冷短波320×256红外焦平面读出电路研制中,本文采用了应用更广泛的快照工作模式,即要求阵列中的所有探测单元同时积分,并将积分信号保存在单元内部后读出。虽然这种模式可以自由调节积分时间,使信号增强,满足高分辨率、高灵敏度、高速红外探测需求;但是在芯片设计中,要求有限的像元面积内包含积分放大电路和采样保持电路。而作者在缺乏参考资料和设计细节的情况下,完成了该芯片的自主设计和流片验证,采用共源共栅(Cascode)电容反馈跨导放大(CTIA)结构代替传统两级运放CTIA,并同时在30×30μm2像元面积内集成采样保持电路、缓冲器、反饱和功能,实现了快照式读出,通过调节积分电容和积分时间,可将动态范围成倍扩展。同时,基于格雷码原理设计的控制电路,实现了动态窗口读出,图像翻转,1、2、4路输出等多种实用功能。更多还原

【Abstract】 Compared with cooled infrared imaging systems, uncooled infrared imaging system can work at room temperature and greatly reduces the system size, cost and power consumption because of eliminating the heavy and expensive cooling equipment.In addition, it also provides a wider spectral response and longer life time. Foreign infrared imging systems institutions have already developed a large number of lower cost, higher reliability, high sensitivity uncooled infrared imager for military users. However, uncooled infrared imaging research and development started late and also constrained by industrial foundation in China, the technology is far behind of foreign countries. But the market demand is increasing, so the development of uncooled infrared imaging technology has become essential. Based on the above background, research on design and implementation of CMOS focal plane readout circuit (ROIC), which is the core device of uncooled infrared imaging system, had been proceeded in this paper.After a thorough understanding of domestic and foreign latest research work, the author proceeded the state 973 XXX project (ID: 51313XXX) as the main researcher. In the project, a monolithic 320×240 uncooled pyroelectric infrared focal plane array (IRFPA) readout circuit was independent designed and verified. Especially, in order to solve thermal budget dilemma encountered in the case of backend processing temperature of monolithic integration, the high-temperature resisted process of ROIC had been designed and implemented independently. Then as the main researcher, the author designed and developed the other two ROICs which have broad market prospects as pyroelectric ROIC, that is uncooled microbolometer 160×120 IRFPA ROIC and uncooled shortwave 320×256 multi-function snapshot IRFPA ROIC.In the above research, different detector types mean different ROIC structures, so after full consideration of schematic, layout, process and interface to detector, the main contribution and innovation are as follows:First, in the research work on ferroelectric-based uncooled infrared ROIC, a refractory metal and silicide connection structure compatible with standard CMOS process was proposed. By the large array of 320×240 readout circuit design, silicon verification and test, a good high temperature properties of low resistance interconnect structure was obtained, and with this new interconnect process utilized in standard CMOS procedures, thermal budget dilemma encountered in the case of backend processing temperature of monolithic integration can be addressed. This method has not been reported at home and abroad, Chinese patent had been applied and authorized, Patent No.: 200610021450.4.Second, for pyroelectric detector is a high impedance capacitive component, a Resistive Trans-impedance Amplifier (RTIA) readout circuit for Uncooled Focal Plane Array (UFPA) using active resistor was proposed in this paper. By using a sub-threshold MOSFET as a 1011? and above feedback resistor, a high gain current amplifier can be realized by common source structure which consisted of two transistors. The simple three transistors can be easily integrated under pixel and it has good impedance matching with pyroelectric infrared detector. Compared with traditional RTIAs which use special high-resistance materials as feedback resistor, the novel RTIA is low cost because no additional materials and processes are needed.Third, based on RTIA described before, a RTIA for UFPA using native MOS was proposed. Because no additional mask in native MOS process, and compared to the enhanced MOS working in the subthreshold region, native MOS gate was directly connected to ground, therefore, the large resistance was stable and bias circuit was eliminated.Fourth, during the research and development of shortwave 320×256 IRFPA ROIC, snapshot mode was used, and it required that all array elements integrated simultaneously, then all integration signals stored in the unit and read out. Although this mode can freely adjust integration time, enhance the signal to meet the high-resolution, high sensitivity, high-speed infrared detection needs; but in chip design, the integration amplifier and sample and hold circuit will be contained in a limited area of each pixel. It means great difficult will meet in the chip design. And the ROIC was designed and verified in the absence of reference documents and design details. By using Cascode CTIA to replace traditional two stage operational amplifier CTIA, the integration amplifier, buffer, anti-blooming, sample and hold were contained in the 30×30μm2 pixel area and snapshot mode was realized. Through adjustable integration time and capacitors, the dynamic range can be extended efficiently. Based on the Gray code theory, random window access, dynamic image transposition, and 1, 2, 4 selectable channel outputs, can be realized by digital control circuits of the ROIC.更多还原