原子钟作为现行稳定度和准确度很高的时频基准，被广泛应用于科学测量、授时定位导航等领域。传统的原子钟一般体积大（100cm3级）、功耗高（kW级）、不具备便携性。基于相干布居囚禁（coherent population trapping，CPT）原理的CPT原子钟具有全光结构、无需谐振腔的特点，系统结构可以实现微型化，降低其体积、功耗，提高便携性。通过微机电系统（micro-electro-mechanical system, MEMS）和集成电路（integrated circuit, IC）技术，系统可进一步集成得到芯片级原子钟（chip-scale atomic clock, CSAC）。CSAC因其体积小、功耗低、成本低、更具便携性的特点扩展了高精度时钟的应用范围，在同步通讯、定位导航、自然探测等军用民用领域都有着良好的应用前景。CSAC与传统的MEMS器件不同，其以碱金属气室为核心的物理系统集成工艺，涉及光机电热磁等多种影响因素，决定了CSAC的性能及系统微型化程度。本论文主要围绕MEMS碱金属蒸气腔室的集成设计与制造工艺，构建芯片级原子钟物理集成系统，研究对CPT信号的分析、测试与优化。基于MEMS技术为腔室集成加热器和温度传感器等功能组件，在玻璃表面形成对称双线布线结构的金属加热图形实现无磁加热；后通过阳极键合工艺和Ne气引入，得到7.5×5×1.9mm3大小的玻璃-硅-玻璃三层结构集成碱金属蒸气腔室，漏率10-9Pa?m3/s量级。本论文设计并实现了使用PCB柔性复合板实现集成腔室表面电极与外部电路的联通，通过控制系统加热升温至80℃并稳定控温，气室温度波动小于0.1K，系统的加热总功耗为42mW。选用环氧树脂作为封装材料，设计封装外壳实现光学镜组的固定封装，获得尺寸大小为20×15×23mm3、6.9cm3的芯片级原子钟物理系统，测试获得CPT信号线宽为2.1kHz。本论文研究了光强、微波调制功率、温度等物理参数对CPT信号及原子钟系统的影响，得到原子钟系统稳定度更高的工作条件与参数，为后续物理系统集成提供了指导。
Atomic clocks are widely used in scientific measurement, timing, positioning, navigation and other fields as time-frequency standards with the high stability and accuracy. Traditional atomic clocks have the characteristics of large size (100cm3 level), high power consumption (kW level) and inconvenience. Based on the theory of coherent population trapping (CPT), CPT atomic clock has an all-optical structure without any cavity, which can be miniaturized. With the application of micro-electro-mechanical system (MEMS) and integrated circuit (IC) technology, the system can be further integrated to obtain the chip-scale atomic clock (CSAC). Because of its small size, low power consumption, low cost and more portability, CSAC has expanded the range of applications of high-precision clocks and has a good application prospect in synchronous communication, positioning and navigation, natural detection for military and civil use. Different from traditional MEMS devices, CSAC's physical system integration process, taking the alkali vapor cell as the core, involves various factors such as optical, electromechanical, thermal and magnetic, which determines the performance of CSAC and the degree of system miniaturization. This article mainly focuses on the integrated design and fabrication of the MEMS alkali vapor cell, and builds the physics system of the chip-scale atomic clock and a desktop experimental system to test, analyze and optimize the CPT signal. Based on MEMS technology the cell is integrated with the heater and temperature sensor components. We sputter and lift off to obtain platinum graphics on a glass surface and use the symmetrical double wiring structure for achieving non-magnetic heating. After anodic bonding and bringing in buffer gas, a glass-silicon-glass integrated alkali vapor cell with a size of 7.5×5×1.9mm3 is obtained, and the leakage rate is about 10-9Pa?m3/s. A flexible PCB composite board was designed and fabricated to connect the surface metal pads with the external circuit. The system was heated to 80℃, which consumes 42.4mW and the temperature fluctuation was stabilized in the range of less than 0.1K. Epoxy resin was used as the packaging material, and the packaging shell was designed to realize the fixed packaging of optical mirror set. The chip atomic clock physical system with the size of 20×15×23mm3 and the volume of 6.9cm3 was obtained. Finally, the CPT spectrum signal with line width of 2.1kHz was obtained. The effects of physical parameters like light intensity, microwave modulation power and temperature on CPT signal and atomic clock system were studied, and the working conditions and parameters of the atomic clock system with higher stability were obtained, which provides guidance for subsequent physical system integration.
