SBIR Phase II: Novel Wafer Fabrication Technology for Semiconductor Sensors

该小型企业创新研究（SBIR）二期项目旨在通过使用离子束层分离工艺从大块单晶中分离出碲化镉锌（CdZnTe）单晶薄膜。分离的层将被转移并粘合到硅（Si）晶片上，作为碲化汞镉（HgCdTe）薄膜外延生长的衬底。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状晶体中制造大量薄膜，从而为红外探测器材料提供经济的晶圆生产技术。高能（MeV）光离子将用于在大块晶体中产生埋藏的损坏层。在高温下的热退火可能产生使层分离的侧向裂纹。第一阶段已经证明了这种方法的可行性。第二阶段的研究目标是优化晶圆级分离的工艺参数，并开发将分离的薄膜转移到硅片上的工艺。由此制备的晶圆将用于HgCdTe的外延生长和红外探测器的制造。CdTe和（Cd,Zn）Te合金晶体的生长采用了各种技术，包括区域精炼、垂直梯度冷冻（VGF）、液体封装法（LEC）、水平和垂直Bridgman技术。由于产量变化，这些方法都没有产生足够的材料与质量需要今天的红外（IR）探测器的应用。所提出的方法是为了克服这些限制而开发的。在商业上，该技术的优点是通过离子束切片从单个块状晶体中生产出许多高质量的衬底，从而提供了一种生产可靠和可复制的高质量材料的经济方法。此外，通过在更便宜的Si衬底上以地砖模式堆叠更小的薄片，可以实现用于HgCdTe生长的大面积CdZnTe衬底。与硅衬底的结合也将使红外探测器与电子器件集成在一个芯片上。红外光电探测器和焦平面阵列在许多工业和科学应用中引起了人们的兴趣，包括环境监测、化学生物检测、医疗和空间传感器。

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.