Grants and Contributions:

Grant or Award spanning more than one fiscal year (2017-2018 to 2018-2019).

For novel X-ray detectors, amorphous Selenium films are used on top of semiconductor substrates inx000D
combination with integrated circuits. Electrical connections to the Selenium layer are needed for operation.x000D
Typically, fine wires are used. The requirements for joining of the fine wires to the Selenium include lowx000D
temperature (room temperature ideally), no organic adhesive reacting with Selenium, and small size as thex000D
joints should not obstruct the X-ray images.x000D
Microelectronic wire bonding is the main technology to interconnect to integrated circuits. Existing lowx000D
temperature processes of wire bonding are suggested for this project. Wire bonds have 100 % metallic naturex000D
and are very small but do not stick to all surfaces. To facilitate wire bonding, the Selenium is coated with a thinx000D
Gold layer. However, as the Gold coating is thin and the Selenium layer quite soft, wire bonding often resultsx000D
in non-sticking failure. The bonds that stick might not be reliable in the long run.x000D
The development of a consistent low temperature wire bonding process and its reliability evaluation isx000D
proposed in this project to achieve the electrical connection of bonding wire to Gold coated Selenium. Thisx000D
process will allow the development of miniaturized and high resolution X-ray detectors with sufficient pixels.x000D
The project will adopt an improved design-of-experiment methods for the process development combined withx000D
reliability methods such as novel current stressing and real time resistance monitoring systems recentlyx000D
developed at the University of Waterloo. In contrast to other joining methods such as conductive adhesives andx000D
soldering, a successfully developed low temperature wire bonding process to Selenium will maximize thex000D
performance of the X-ray detector. The findings from the process development and reliability evaluation willx000D
add to the knowledge on wire bonding technology in general.