SBIR Phase II: Novel Wafer Fabrication Technology for Semiconductor Sensors

该小型企业创新研究(SBIR)第二阶段项目旨在通过使用离子束层分离工艺从大块单晶中开发碲化锌镉(CDZnTe)单晶薄膜。分离的层将被转移并结合到硅(Si)晶片上，作为衬底用于外延生长碲化镉汞(HgCdTe)薄膜。HgCdTe薄膜是红外探测器的研究热点。离子束层分离工艺将允许从单个块体晶体制造大量薄膜，从而为红外探测器材料提供经济的晶片生产技术。高能(MeV)轻离子将被用来在大块晶体中产生埋藏的损伤层。高温热退火可能会产生侧向裂纹，从而导致层分离。第一阶段已经证明了这一方法的可行性。第二阶段的研究目标是优化晶片规模不破裂分离的工艺参数，并开发将分离出的薄膜转移到硅片上的工艺。所制备的晶片将用于HgCdTe的外延生长和红外探测器的制作。采用区域精炼法、垂直梯度冷冻法、液封提拉法、水平布里奇曼法和垂直布里奇曼法等不同的方法生长了Cd Te和(Cd，Zn)Te合金晶体。由于产量的变化，这些方法都没有生产出足够的材料来满足今天的红外(IR)探测器应用所需的质量。提出的方法就是为了克服这些限制而开发的。在商业上，所提出的技术的优点是通过离子束切片从单个块体晶体中生产出许多高质量的衬底，从而提供了一种经济的方法来生产可靠和可重复的高质量材料。此外，通过在更便宜的硅衬底上以地砖图案堆叠更小的片层，将有可能实现用于生长HgCdTe的大面积CdZnTe衬底。与硅衬底的结合还将允许在单个芯片上集成红外探测器和电子设备。红外光电探测器和焦平面阵列在包括环境监测、化学生物检测、医疗和空间传感器在内的许多工业和科学应用中具有重要意义。

This Small Business Innovation Research (SBIR) Phase II project is directed toward the development of cadmium zinc telluride (CdZnTe) single crystal films by using an ion beam layer separation process from bulk single crystals. The separated layers will be transferred and bonded on to silicon (Si) wafers for applications as substrates for epitaxial growth of mercury cadmium telluride (HgCdTe) films. HgCdTe films are of interest in infrared detectors. The ion beam layer separation process will allow the fabrication of a large number of films from a single bulk crystal, thus providing an economical wafer production technology for infrared detector materials. High-energy (MeV) light ions will be used to produce a buried damaged layer in the bulk crystal. Thermal annealing at elevated temperatures may generate lateral crack enabling the layer separation. Phase I has shown the feasibility of this approach. Phase II research objectives are to optimize the process parameters for wafer-scale separation without breaking and develop the process to transfer the separated films on to Si wafers. The wafers thus fabricated will be used for epitaxial growth of HgCdTe and fabrication of IR detectors. CdTe and (Cd,Zn)Te alloy crystals have been grown by various techniques including zone refining, vertical gradient freeze (VGF), liquid encapsulated Czochralski (LEC) methods, horizontal and vertical Bridgman techniques. Due to variable yields, none of these methods have produced enough material with the quality needed for today's infrared (IR) detector applications. The proposed method has been developed to overcome these limitations.Commercially, the proposed technique has the advantage of producing many good quality substrates from a single bulk crystal by ion beam slicing, thus providing an economic way of producing reliable and reproducible quality material. Also, large area CdZnTe substrate for the growth of HgCdTe will be possible by stacking smaller slices in a floor tile pattern on cheaper Si substrates. Bonding with Si substrate will also allow the integration of IR detectors with electronics on a single chip. IR photodetectors and focal plane arrays are of interest in many industrial and scientific applications including environmental monitoring, chem-bio detection, medical and space sensors.