Shuichi Shoji

Vacuum packaging for microsensors by glass-silicon anodic bonding

Abstract Vacuum packaging by the glass-silicon anodic process is studied. The residual gas generated during the anodic binding process and that desobed from the silicon and glass surface increase the pressure in a sealed cavity. In order to fabricate a vacuum sealed cavity, two methods are proposed to eliminate the residual gas; (i) the residual gases are evacuated through a small opening after bonding and then the opening is plugged by depositing a material in vacuum, (ii) the residual gases are absorbed by a getter inside the sealed cavity. A non-evaporable getter (NEG) is used for the second method. A vacuum sealing of tens of Torr is obtained by the firat method. The second method and a combnation of the two methids enables vacuum sealing at a pressure lower than 10-5Torr. A prototype of a capacitive vacuum sensor is fabricated by using the second method.

Normally close microvalve and micropump fabricated on a silicon wafer

A normally closed microvalve and micropump were fabricated on a silicon wafer by micromachining techniques. Normally closed microvalve has a silicon diaphragm and a small piezoelectric actuator to drive it. The controllable gas flow rate is from 0.1 ml/min to 85 ml/min at a gas pressure of 0.75 kgf/cm/sup 2/. The micropump is a diaphragm-type pump which consists of two polysilicon one-way valves and a diaphragm driven by a small piezoelectric actuator. The maximum pumping flow rate and pressure are 20 mu l/min and 780 mmH/sub 2/O/cm/sup 2/, respectively.<<ETX>>

Micropump and sample-injector for integrated chemical analyzing systems

Abstract A dual pump and a buffer pump have been integrated on a silicon wafer for chemical analyzing systems. These pumps realize constant and rippleless liquid flow of a small volume. The controllable flow rate of the pumps was up to about 40 μl/min and the maximum pumping pressure was about 1 mH2O. A sample injector made up of two three-way valves has also been fabricated with micromachining.

Normally closed microvalve and mircopump fabricated on a silicon wafer

Abstract A normally closed microvalve and a micropump are fabricated on a silicon wafer by micro-machining techniques. The normally closed microvalve has a movable silicon diaphragm and a small piezoactuator to drive it. The controllable gas flow rate is from 0.1 ml/min to 85 ml/min at a gas pressure of 0.75 kgf/cm 2 . The micropump is a diaphragm-type pump, which consists of two polysilicon one-way valves and a diaphragm driven by a small piezoactuator. The maximum pumping flow rate and pressure are 20 μ/min and 780 mmH 2 O respectively.

Smallest dead volume microvalves for integrated chemical analyzing systems

Normally open, normally closed, and three-way microvalves were developed. These microvalves had a simple structure and small dead volume on the order of tens of nl. Each microvalve was driven by a stack-type piezo-actuator and the controllable flow range is from 1 mu l/min to tens of mu l/min. These valves are useful for constructing integrated chemical analyzing systems.<<ETX>>

Prototype miniature blood gas analyser fabricated on a silicon wafer

Abstract The fabrication of a miniature blood pH monitoring system formed on a silicon wafer using a pH ISFET and a new type of micro-valve actuator is described. The system samples the blood from the vein, measures its pH and calibrates zero drift of the sensor automatically and periodically. The main body of the system, the micro-cell, is made of a silicon wafer and a Pyrex glass plate processed by IC technology (micro-machining). This cell is significantly smaller, lighter and more portable than presently available blood gas analysers, in particular, the sample volume reduction is a very distinctive feature of it. The total necessary sample volume of the system is about 10 μl.

A micro chemical analyzing system integrated on a silicon wafer

The fabrication of a three-way valve on a silicon wafer by micromachining techniques is presented. The valve consists of two silicon wafers, a pyrex glass, and a piezoelectric actuator. This three-way valve can control gas flow or liquid flow with voltage applied to the actuator. The liquid flow can be controlled from 0.1 mu l/min to 70 mu l/min. The results from integrating the three-way valve with a micropump to produce a flow injection analyzing system are discussed.<<ETX>>

Micro flow cell for blood gas analysis realizing very small sample volume

Abstract A micro flow cell for blood gas monitoring is fabricated on a silicon wafer to realize a very small sample volume. It has a Clark-type micro P O 2 sensor, a Severinghaus-type micro P CO 2 sensor and an ISFET-type pH sensor. The cell size is 1.0 cm × 0.6 cm × 0.8 cm and the necessary sample volume is about 0.34 μl.

Low-temperature silicon-to-silicon anodic bonding with intermediate low melting point glan

Abstract Room-temperature silicon-to-silicon bonding has been performed. It is an electrostatic bonding using sputtered low melting point glass as an intermediate layer. Wafers can be bonded at room temperature with an applied voltage of about 50 V. This technique is useful for the fabrication of intelligent sensors and microelectromechanical systems.

Fabrication and packaging of a resonant infrared sensor integrated in silicon

Abstract A novel integrated infrared (IR) sensor is described that incorporates a resonant silicon/silicon dioxide microbridge. The resonance frequency of the microbridge is sensitive to the incident IR power as a result of the thermally induced stress variation resulting from the absorption of the IR radiation. A merged process including on-wafer stress-free packaging, NMOS circuitry and bulk silicon micromachining is illustrated. One-port electrostatic excitation and capacitive detection was used, the resonator being electrically floating. Relative responsitivities of 450 ppm/μW of absorbed power were obtained.