Low-k integration: Gas screening for cryogenic etching and plasma damage mitigation

The integration of porous organo-silicate low-k materials has met a lot of technical challenges.One of the main issues is plasma-induced damage,occurring for all plasma steps involved during interconnects processing.In the present paper,we focus on porous SiOCH low-k damage mitigation using cryogenic temperature so as to enable micro-capillary condensation.The aim is to protect the porous low-k from plasma-induced damage and keep the k-value of the material unchanged,in order to limit the RC delay of interconnexion levels while shrinking the microchip dimension.The cryogenic temperature is used to condense a gas inside the porous low-k material.Then,the etching process is performed at the temperature of condensation in order to keep the condensate trapped inside the material during the etching.In the first part of this work,the condensation properties of several gases are screened,leading to a down selection of five gases.Then,their stability into the porous structure is evaluated at different temperature.Four of them are used for plasma damage mitigation comparison.Damage mitigation is effective and shows negligible damage for one of the gases at-50℃.

Microelectronic neural bridge for signal regeneration and function rebuilding over two separate nerves

According to the feature of neural signals,a micro-electronic neural bridge（MENB）has been designed. It consists of two electrode arrays for neural signal detection and functional electrical stimulation（FES）,and a microelectronic circuit for signal amplifying,processing,and FES driving.The core of the system is realized in 0.5-μm CMOS technology and used in animal experiments.A special experimental strategy has been designed to demonstrate the feasibility of the system.With the help of the MENB,the withdrawal reflex function of the left/right leg of one spinal toad has been rebuilt in the corresponding leg of another spinal toad.According to the coherence analysis between the source and regenerated neural signals,the controlled spinal toad＇s sciatic nerve signal is delayed by 0.72 ms in relation to the sciatic nerve signal of the source spinal toad and the cross-correlation function reaches a value of 0.73.This shows that the regenerated signal is correlated with the source sciatic signal significantly and the neural activities involved in reflex function have been regenerated.The experiment demonstrates that the MENB is useful in rebuilding the neural function between nerves of different bodies.

THREE-ELECTRODE HIGH-TEMPERATURE OXYGEN SENSOR

Using micro-electronic techniques, a high-temperature oxygen sensor with three electrodesis designed. Yttrium-doped stabilized zirconia is used to make the solid electrolyte and thesupporting substrate for the electrodes. A gold resistance thermometer is installed on thesensor to directly monitor the temperature of gas. The platinum film is covered with aporous alumina coating, to reduce the flow effect on the sensor output and prolong thesensor’s life. Tests, conducted at 650-900℃ in the mixture of oxygen and nitrogen withthe spanning 0-32.7% oxygen concentration, indicate that the sensor is of higher sensitivity,better reproducibility and durability, fast response, but relatively large current outputs areachieved simultaneously. The sensor fabricated using photolithographic reduction and thick-film metallization techniques is conductive to substantial miniaturization.