Polymer-CMOS Hybrid Neural Probes for Large-Scale Neuro-Electronic Interfacing

Achieving a stable, long-term connection with millions of neurons within living organisms remains one of the dreams of neuroscience. Silicon shank based probes lead the field in terms of pure channel count. On the other hand, polymer neural probes offer superior biocompatibility, ruggedness and lower cost. This work tries to merge these technologies while exploring new electronic and interconnect design methods, ultimately yielding a prototype of a polymer-CMOS hybrid neural probe with a gold bump interconnect along with an electronic design based on bipolar transistor input devices, pseudo-capacitive AC coupling and in-pixel digitization.

Development of a New Wire Bonding Technology on Integrated Circuit Devices

In IC packaging, copper wire is generally regarded as a competent successor to gold wire due to many advantages in mechanical characteristics and cost efficiency. However, its known disadvantages restrict it to low-end integrated circuits as well. This paper discusses the development of a new wire bonding technology — copper ball on gold bump (COG) bonding in current wire bonders with both 1 mil copper and gold wires. It covers material and tool selection, wire bonding process window development, electrical characterization and reliability studies. The material and tool selection includes copper wire, experimental chip, capillary and wire bonder. Process window development focuses on two crucial stages, copper free air ball (FAB) formation and bonding process window development for both gold bump and copper ball bonded on Au bump. DOE approach is introduced into the relative process developments. The experimental studies reveal that flow rate of shielding gas is a key factor to obtain the qualified FAB formation and process window optimization for gold bump and copper ball on gold bump is more crucial to develop a successful COG bonding. Wire pull test, ball shear test and crater test are involved in the output measurement based on the criteria of JEDEC during the process window development. Package integrity and reliability performance with the COG bonding are fully assessed by performing electrical characterization and package internal delamination detection on the evaluated samples which have respectively undergone three reliability tests, High Temperature Baking, Temperature Cycle and Autoclave. The study result finally indicates that the COG bonding is a practicable approach to achieving copper wire application to high-end integrated circuits.

Improvement of LDI BUMP Stripping Process by Development of Room Temperature PR Stripper

ABSTRACTBump process using gold bump led to many cleaning problems like polymer residues, metal and polyimide consumption after stripping process. First of all, stripping process of bump photoresist is one of the difficult technologies since thickness of PR pattern of bump is thicker than that of general metal line at least 100 times. We investigated the improvement of LDI BUMP stripping Process at 25 with new chemical. We found that the wettability may be improved when the additive was added to the chemical and it improves the stripping ability. It was found that new chemical was superior to commercial chemical in terms of chemical stability, removal efficiency of polymer residue and decrease in metal and polyimide consumption. Also, we could obtain removal mechanism of photoresist pattern by measured Raman equipment and enhancement of yield in mass production line of semiconductor.