Duck Jung Lee

A novel low-loss wafer-level packaging of the RF-MEMS devices

In this work, the flip-chip method was used for packaging an RF-MEMS switch on a quartz substrate with low losses. 4-inch Pyrex glass was used as a package substrate and was airblast punched with 250 /spl mu/m diameter holes. A Cr/Au seed layer was deposited on it and the vias were filled by plating with gold. After forming molds on the holes with thick photoresist, bumps were plated on holes. The package substrate was bonded with a quartz substrate using B-stage epoxy. The loss of the overall package structure was tested with a network analyzer and was within -0.05 dB. This structure can be used for wafer level packaging of both RF-MEMS and other MEMS devices.

Effects of a hydrophilic surface in anodic bonding

This paper presents a study of the anodic bonding technique using a hydrophilic surface. Our method differs from conventional processes in the pre-treatment of the wafer. Hydrophilic surfaces were achieved from dipping in H2O/H2O2/NH4OH solution. The hydrophilic surface has a large number of -OH groups, which can form hydrogen bonds when two wafers are in contact. This induces a higher electrostatic force, because of the decreasing gap between the glass and silicon wafer. We achieved improved properties, such as a wider bonded area and a higher bond strength than those of conventional methods. Also, the fabricated pressure sensors on the 5-inch silicon wafer were bonded to Pyrex #7740 glass of 3 mm thickness. In order to investigate the migration of the sodium ions, the depth profile at the glass surface by secondary-ion mass spectroscopy and the bonding current were compared with that of conventional methods.

Glass- to-glass anodic bonding for high vacuum packaging of microelectronics and its stability

In this work, we have developed a new high vacuum packaging method using a glass-to-glass bonding for the application to microelectronic devices such as field emission display (FED). The glass-to-glass anodic bonding was established and optimized using introducing thin amorphous silicon (a-Si) interlayer. Also, we propose that the amount of oxygen ions is one of the important factors during the bonding process, as confirmed from the SIMS and XPS analyses for the reaction region of Si-O bond in interface. Our method was very effective to reduce the bonding temperature and make the high vacuum package of microelectronic devices over 10/sup -4/ Torr. Finally, to evaluate the vacuum sealing capability of a FED panel packaged by the method, the leak characteristics of the vacuum was examined by spinning rotor gauge (SRG) during 6 months and the electron emission properties of the panel were measured continuously for time variation during 26 days.

A novel thin chip scale packaging of the RF-MEMS devices using ultra thin silicon

In this paper, as ultra thin silicon substrate was used as packaging substrate, we proposed ultra thin chip size RF-MEMS packaging technology that has vertical feed-through for low loss, as reduced the parasitic capacity. Thin silicon wafer with 50um thickness was fabricated to achieve short electric path, low loss and lightweight. And then via holes with the diameter of 60um were fabricated and was filled by the RIE and electroplating process. Also, the wafer level bumps were fabricated for simple, low cost, and fine patterning process. The measured S-parameter of packaged CPW(Co-planner waveguide) has the reflection loss of under -19 dB and the insertion loss of -0.54 to -0.67 dB.

Novel Bonding Technology for Hermetically Sealed Silicon Micropackage

We performed glass-to-silicon bonding and fabricated a hermetically sealed silicon wafer using silicon direct bonding followed by anodic bonding (SDAB). The hydrophilized glass and silicon wafers in solution were dried and initially bonded in atmosphere as in the silicon direct bonding (SDB) process, but annealing at high temperature was not performed. Anodic bonding was subsequently carried out for the initially bonded specimens. Then the wafer pairs bonded by the SDAB method were different from those bonded by the anodic bonding process only. The effects of the bonding process on the bonded area and tensile strength were investigated as functions of bonding temperature and voltage. Using scanning electron microscopy (SEM), the cross-sectional view of the bonded interface region was observed. In order to investigate the migration of the sodium ions in the bonding process, the concentration of the bonded glass was compared with that of standard glass. The specimen bonded using the SDAB process had higher efficiency than that using the anodic bonding process only.

Packaging of the rf MEMS switch

In this work, the flip-chip method was used for packaging of the RF-MEMS switch on the quartz substrate with low losses. The 4-inch Pyrex glass was used as a package substrate and it was punched with airblast with 250 micrometers diameter holes. The Cr/Au seed layer was deposited on it and the vias were filled with plating gold. After forming the molds on the holes with thick photoresist, the bumps were plated on holes. The package substrate was bonded with the quartz substrate with the B-stage epoxy. The loss of the overall package structure was tested with a network analyzer and was within -0.05 dB. This structure can be used for wafer level packaging of not only the RF-MEMS devices but also the MEMS devices.

Application of Electrostatic Bonding to Field Emission Display Vacuum Packaging

A tubeless packaging technology for field emission display (FED) devices is developed using indirect glass-to-glass electrostatic bonding with an intermediate amorphous silicon layer at a low temperature of 230°C. The glass-to-glass bonding mechanism is investigated by secondary-ion mass spectroscopy. To evaluate the vacuum sealing capability of a FED panel packaged by this method, the leak characteristics of the vacuum were examined by spinning rotor gauge for 6 months and the electron emission properties of the panel was measured continuously for different amounts of time over a 26 day period. In order to examine the effect of the removal of the exhausting tube on the enhancement of vacuum efficiency, we have calculated a theoretical vacuum level in the panel based on conductance and throughput and compared with experimental values.

New plasma display panel packaging technology using electrostatic bonding method

In this work, we have developed a plasma display panel (PDP) packaging technology, replacing the tip off tube with an indirect glass-to-glass electrostatic bond with intermediate layers of indium tin oxide and amorphous silicon. The glass-to-glass bonding for the packaging was performed at a low temperature of 180 °C while applying a bias of 250 Vdc in an environment of three mixed gases: He–Ne(27%)–Xe(3%). The 3.6 in. color alternating current-PDP with 8 mm thickness was successfully fabricated, with full white color brightness at a firing voltage of 190 V. Additionally, the luminance during the sustained period was 900–1000 cd/m2. To investigate the capability of applying the glass bonding technology, the hermetic sealing test of the packaged panel was examined by a spinning rotor gauge for time variation. The leak rate test was performed with a helium detector. Since there is very low leakage through the bonded interface during 160 h, we can propose that it is highly possible to apply this technology t...

Thin AC-PDP Vacuum In-line Sealing Using Direct-Joint Packaging Method

In this work, we have improved vacuum in-line sealing technologies for plasma display panels (PDPs) using the direct-joint packaging method, which is different from the conventional packaging method in the aspects of exhaust hole and tube. We use the glass frit and B-stage organic binder materials for packaging. The sintering process is performed for both materials before packaging to reduce out-gassing and to optimize conditions. To get the high vacuum conductance, we suggest the lump structure on seal-line. The vacuum conductance using lump structures provides better pumping efficiency than tube packaging by theoretical calculation. The packaging temperatures for glass frit and organic binder are 380 and 175°C, respectively. The 4 in. alternating current (ac)-PDP is successfully packaged in He-Ne(27%)-Xe(3%) ambient and fully emitted with brightness of about 1000 cd/m 2 . The long-term reliability of packaged PDP is evaluated through both the light emission characteristics and a driving test for one year. This method has the advantages of a simple, brief, low cost process, improved gas uniformity by high vacuum efficiency, and thin panel fabrication achieved by the removal of the exhaust hole and tube.

Evaluation of carbon nanotubes as gas sensing materials in micro gas sensors

We fabricated the gas sensor using carbon nanotubes (CNTs) and investigated the detection properties for NH/sub 3/ gas. The sensing material of gas sensor is employed multi-wall carbon nanotubes (MWNTs). The CNT gas sensor structure is realized with technologies of micro-electro mechanical systems (MEMS). The nanotubes gas sensor is operated at room temperature. And the electrical resistance of the carbon nanotubes is measured upon exposure to NH/sub 3/ gases. Also, recovery time of CNT gas sensor is measured according to temperature.