The adhesion durability of coatings and encapsulant materials utilized in electronic packaging is vital for device reliability in the microelectronics industry. Due to adverse operating conditions such as high moisture and high temperature environments, the adhesion between an adhesive and its substrate is typically compromised. This thesis addresses the advantages of employing plasma pretreatments and surface derivatization using silane coupling agents as surface modification techniques in an effort to enhance the adhesive bonding of epoxy to SiC coated Si wafers (SiC/Si). Durability was evaluated by immersing coated-Si samples in aqueous solutions at elevated temperature (60°C) to simulate prolonged severe operating conditions. Three surface modification approaches for the SiC/Si substrate to be discussed include: 1) a silane coupling agent treatment, which involves a reaction of either 3-aminopropyltriethoxysilane (APS) or 3-glycidoxypropyltrimethoxysilane (GPS) with the substrate, 2) an oxygen plasma pretreatment followed by a silane treatment, and 3) a water/oxygen plasma pretreatment followed by a silane treatment. Samples were immersed in aqueous solutions at various pH at 60°C for extended periods of time. Adhesion durability of treated epoxy/SiC/Si systems was qualitatively evaluated by visual inspection for debonding, and quantitatively evaluated using a probe test to evaluate the critical strain energy release rate G_c. Additionally, X-ray photoelectron spectroscopy (XPS) surface characterization was carried out following the surface treatments and again after complete failure in the durability tests. The durability tests illustrated that surface treatments involving an oxygen plasma pretreatment prior to silane derivatization resulted in significant improvement in adhesive performance. Furthermore, the results of XPS analysis suggested that the improved bonding was due to cleaning of the substrate surface, promotion of silane adsorption and the formation of a thicker oxide layer. The effectiveness of the surface modification methods in relationship to surface chemistry and adhesion for the epoxy/SiC/Si system is reported and discussed in this work. / Master of Science

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

No description available.

No description available.

by Chen Dihu. / "November 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 160-173). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Electronic power devices made of silicon carbide promisesuperior performance over today's silicon devices due toinherent material properties. As a result of the material'swide band gap of 3.2eV, high thermal conductivity, itsmechanical and chemical stability and a high critical electricfield, 4H-silicon carbide devices have the potential to be usedat elevated temperatures and in harsh environments. Shortercarrier lifetimes and a reduction in the necessary width of thelow-doped drift zone in silicon carbide devices compared totheir silicon counterparts result in faster switching speedsand lower switching losses and thus in much more efficientpower devices. High-voltage 4H-silicon carbide diodes have been fabricatedin a newly developed processing sequence, using standardsilicon process equipment. Epitaxial layers grown by chemicalvapor deposition (CVD) on commercial 4H-silicon carbidesubstrates were used as starting material for both mesa-etchedepitaxial and implanted p+n-n+ planar diodes, Schottky diodesand merged pn-Schottky (MPS) diodes, together with additionaltest structures. The device metallization was optimized to givea low contact resistivity on implanted and epitaxial layers anda sufficiently high Schottky barrier with a singlemetallization scheme. Different high-field termination designshave been tested and breakdown voltages of up to 4 kV onimplanted, field-ring terminated diodes were achieved,corresponding to 80% of the critical electric field. A 5kVepitaxial diode design with a forward voltage drop of 3.5V at acurrent density of 100Acm-2 equipped with an implanted junctiontermination extension (JTE) was also fabricated. A new measurement setup was designed and built with thecapability of measuring current-voltage and capacitance-voltagecharacteristics of semiconductor devices at reverse biases upto 10kV. Together with these electrical measurements, theresults of other characterization techniques were used toidentify performance limiting defects in the fabricated siliconcarbide diodes. Increased forward voltage drop of bipolardevices during on-state operation was studied and it was shownthat the stacking faults causing forward degradation arevisible in scanning electron microscopy. With the help ofsynchrotron white-beam X-ray diffraction topographs (SWBXT),electron beam induced current (EBIC) and electroluminescencemeasurements of silicon carbide diodes, the role of screwdislocations as a dominant source of device failure in the formof localized microplasma breakdown was identified. Screwdislocations with and without open core have been found tocause a 20-80% reduction in the critical electric field of4H-silicon carbide diodes, both for low-voltage (150V) andhigh-voltage (~5kV) designs. While micropipes have almost beeneliminated from commercial silicon carbide material,closed-core screw dislocations are still abundant withdensities in the order of 10000cm-2 in state-of-the-art siliconcarbide epitaxial layers.

In this thesis, high density plasma chemical vapor deposition (HDPCVD) is used to fabricate novel multiple quantum well structure of light emitting diodes (LEDs) and charge storaged layers of SONOS nonvolatile semiconductor memories (NVSMs). On the study of the light emitting diodes (LEDs) technology, wide band gap hydrogenated amorphous silicon carbide and porous silicon carbide has blue or green luminescence are currently being investigated for applications in optoelectronic devices. However, due to the indirect band gap character, the quantum efficiency of these LEDs is very low. In our experiment, we fabricate 5-periods hydrogenated amorphous silicon carbide multiple quantum well structure to enhance the luminescence efficiency. In our study, there are some following notable features: (1) The a-SixC1-x multiple quantum well structure prepared by high density plasma chemical vapor deposition and it shows visible photoluminescence at room temperature. (2) After fluorine ions implantation and thermal annealing, The PL energy of a-SixC1-x multiple quantum well shift to high energy. (3) The PL intensity of SiO2-barrier SixC1-x multiple quantum well is larger than SiNx-barrier. (4) The film adheres well to glass or Si wafer even at low deposition temperature, e.g. 200 0C by high density plasma chemical vapor deposition. On the study of the silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile semiconductor memories (NVSMs) technology, the SONOS is a multi-dielectric device consisting of an oxide-nitride-oxide (ONO) sandwich in which charge storage takes place in discrete traps in the silicon nitride layer. In addition to silicon nitride as the storage layer, we have studied the oxide/SiC:O/oxide sandwiched structures and thermal oxidation of SiC layer as a storage layer by HDPCVD processes. In our study, there are some following notable features: (1) From the capacitance-voltage and current-voltage characteristics of oxygen-incorporated silicon carbide with different oxygen content, it is observed that the memory window is decreased with increasing the oxygen content. By controlling the oxygen content, a higher breakdown voltage can be achieved. (2) In the study of the oxidation of SiC, it is found that low temperature (800 ¢J) oxidized SiC shows a larger memory window than that of the high temperature (925 ¢J) oxidized SiC by high density plasma chemical vapor deposition.