Development of Wire Bonding Process and Reliability Evaluation for Gold coated Selenium

对于新型x射线探测器，非晶硒薄膜被用于半导体衬底与集成电路的结合。操作需要与硒层进行电气连接。通常使用细线。细丝与硒的连接要求包括低温（理想是室温），无有机粘合剂与硒反应，小尺寸，因为接头不应阻碍x射线图像。微电子线键合是集成电路互连的主要技术。本项目建议采用现有的低温焊线工艺。钢丝键具有100%的金属性质，非常小，但不能粘在所有表面上。为了便于电线粘合，硒被涂上了一层锗层。然而，由于金涂层很薄，硒层很软，电线粘合经常导致不粘故障。从长远来看，粘在一起的债券可能并不可靠。为实现焊线与镀金硒的电气连接，本课题提出了一种低温一致焊线工艺及其可靠性评价。这一过程将允许开发具有足够像素的小型化和高分辨率x射线探测器。该项目将采用改进的实验设计方法进行工艺开发，并结合可靠性方法，如滑铁卢大学最近开发的新型电流应力和实时电阻监测系统。与其他连接方法（如导电粘合剂和焊接）相比，成功开发的硒低温焊丝连接工艺将最大限度地提高x射线探测器的性能。工艺开发和可靠性评估的结果将增加对线键合技术的总体了解。

For novel X-ray detectors, amorphous Selenium films are used on top of semiconductor substrates incombination with integrated circuits. Electrical connections to the Selenium layer are needed for operation.Typically, fine wires are used. The requirements for joining of the fine wires to the Selenium include lowtemperature (room temperature ideally), no organic adhesive reacting with Selenium, and small size as thejoints should not obstruct the X-ray images.Microelectronic wire bonding is the main technology to interconnect to integrated circuits. Existing lowtemperature processes of wire bonding are suggested for this project. Wire bonds have 100 % metallic natureand are very small but do not stick to all surfaces. To facilitate wire bonding, the Selenium is coated with a thinGold layer. However, as the Gold coating is thin and the Selenium layer quite soft, wire bonding often resultsin non-sticking failure. The bonds that stick might not be reliable in the long run.The development of a consistent low temperature wire bonding process and its reliability evaluation isproposed in this project to achieve the electrical connection of bonding wire to Gold coated Selenium. Thisprocess will allow the development of miniaturized and high resolution X-ray detectors with sufficient pixels.The project will adopt an improved design-of-experiment methods for the process development combined withreliability methods such as novel current stressing and real time resistance monitoring systems recentlydeveloped at the University of Waterloo. In contrast to other joining methods such as conductive adhesives andsoldering, a successfully developed low temperature wire bonding process to Selenium will maximize theperformance of the X-ray detector. The findings from the process development and reliability evaluation willadd to the knowledge on wire bonding technology in general.