Passivation and corrosion of microelectrode arrays

Application of silicon based microsensors in electrolyte solutions is hampered by insufficient barrier properties and poor corrosion resistance of common passivation layers used to protect the underlying conducting tracks and microelectronic structures. Therefore, the protectivity of various types of compatible passivation layers (organic polyimide and photoresist films, inorganic mono, duplex and triplex layers based on PECVD silicon oxide and silicon nitride) was investigated and improved on microelectrode arrays exposed to I M NaCI (pH 2 to 10) at 25°C. Duplex SiO 2 /Si 3 N 4 and oxide/nitride/oxide (ONO) triplex layers with optimised nitride PECVD process yielded the best barrier properties. Burying the conducting tracks in the thermal silicon oxide layer improves the performance significantly. Failures of the passivation layers, detected by leak current and layer resistance measurements with subsequent SEM investigation, result from cracking due to intrinsic and extrinsic (less important) mechanical stress, film defects (pinholes, particle inclusions), from chemical, physicochemical and electrochemical reactions (external, internal, sublayer corrosion) and from the combined action of mechanical stress and chemical interaction (stress corrosion cracking).

[1]  J. Maibach,et al.  Computer-aided characterization of the elastic properties of thin films , 1992 .

[2]  B. Nguyen,et al.  Plasma Enhanced Chemical Vapor Deposition of Dielectric Films: Correlation of Stress to Film Structure and Plasma Characteristics , 1990 .

[3]  A. C. Adams,et al.  Characterization of Plasma‐Deposited Silicon Dioxide , 1981 .

[4]  W. A. Pliskin.  Comparison of properties of dielectric films deposited by various methods , 1977 .

[5]  A. Calster,et al.  A comparison between silicon nitride films made by PCVD of N2-SiH4/Ar and N2-SiH4/He , 1985 .

[6]  T. H. T. Wu,et al.  STRESS IN PSG AND NITRIDE FILMS AS RELATED TO FILM PROPERTIES AND ANNEALING , 1992 .

[7]  J. Holleman,et al.  The Relationship between Intrinsic Stress of Silicon Nitride Films and Ion Generation in A 50 KHz RF Discharge , 1988 .

[8]  Wolfgang Kronast,et al.  LPCVD against PECVD for micromechanical applications , 1996 .

[9]  J. Drobek,et al.  Structure and Sodium Migration in Silicon Nitride Films , 1968 .

[10]  T. Michalske,et al.  A Molecular Mechanism for Stress Corrosion in Vitreous Silica , 1983 .

[11]  Karsten Dyrbye,et al.  Packaging of physical sensors for aggressive media applications , 1996 .

[12]  H. Lüth,et al.  Modifications and characterization of a silicon-based microelectrode array , 1999 .

[13]  W. Claassen,et al.  Influence of Deposition Temperature, Gas Pressure, Gas Phase Composition, and RF Frequency on Composition and Mechanical Stress of Plasma Silicon Nitride Layers , 1985 .

[14]  Richard Ulrich,et al.  PECVD silicon and nitride postbond films for protecting bondpads, bonds and bondwires from corrosion failure , 1991, 1991 Proceedings 41st Electronic Components & Technology Conference.

[15]  Hyman Joseph Levinstein,et al.  Thermal stresses and cracking resistance of dielectric films (SiN, Si3N4, and SiO2) on Si substrates , 1978 .

[16]  F. Habraken,et al.  Characterization of Plasma Silicon Nitride Layers , 1983 .

[17]  Piet Bergveld,et al.  PECVD silicon nitride diaphragms for condenser microphones , 1991 .

[18]  R. Lathlaen,et al.  Stress in Thin Films of Silane Vapor‐Deposited Silicon Dioxide , 1969 .

[19]  R. Hintsche,et al.  Biosensors for analytical microsystems , 1995 .

[20]  T. F. Retajczyk,et al.  Elastic stiffness and thermal expansion coefficients of various refractory silicides and silicon nitride films , 1980 .

[21]  W. Lanford,et al.  The hydrogen content of plasma‐deposited silicon nitride , 1978 .

[22]  A silicon-based microelectrode array for chemical analysis , 2000 .

[23]  W. Kern,et al.  Advances in deposition processes for passivation films , 1977 .

[24]  Donald L. Smith,et al.  Mechanism of SiN x H y Deposition from NH 3 ‐ SiH4 Plasma , 1990 .

[25]  Si‐Chen Lee,et al.  Oxidation of silicon nitride prepared by plasma‐enhanced chemical vapor deposition at low temperature , 1994 .

[26]  J. Taylor,et al.  Correlation between Processing, Composition, and Mechanical Properties of PECVD-SiN, Thin Films , 1990 .

[27]  Manfred Paeschke,et al.  Chip-array electrodes for simultaneous stripping analysis of trace metals , 1995 .

[28]  W. Brown,et al.  The Effects of Moisture on Strain Relief of Si‒O Bonds in Plasma‐Enhanced Chemical Vapor Deposited Silicon Dioxide Films , 1997 .

[29]  B. Bunker,et al.  Slow fracture model based on strained silicate structures , 1984 .

[30]  F. Habraken,et al.  Characterization of low‐pressure chemical‐vapor‐deposited and thermally‐grown silicon nitride films , 1982 .

[31]  Insulation Division,et al.  Thin film dielectrics , 1969 .

[32]  Hyman Joseph Levinstein,et al.  Reactive Plasma Deposited Si‐N Films for MOS‐LSI Passivation , 1978 .

[33]  J. Wong.  A Review of infrared spectroscopic studies of vapor-deposited dielectric glass films on silicon , 1976 .

[34]  H. Sankur,et al.  Sorbed water and intrinsic stress in composite TiO2‐SiO2 films , 1989 .

[35]  E. P. Eernisse.  Stress in ion‐implanted CVD Si3N4 films , 1977 .

[36]  William D. Brown,et al.  Correlation of stress behavior with hydrogen-related impurities in plasma-enhanced chemical vapor deposited silicon dioxide films , 1997 .

[37]  W. Brown,et al.  Post-deposition processing of low temperature PECVD silicon dioxide films for enhanced stress stability , 1997 .

[38]  Adele Sassella,et al.  Characterization of silicon dioxide and phosphosilicate glass deposited films , 1993 .

[39]  J. Schultze,et al.  Electrochemical formation and reduction of monomolecular oxide layers on (111) and (100) planes of gold single crystals , 1974 .

[40]  G. M. Samuelson,et al.  The Correlations Between Physical and Electrical Properties of PECVD SiN with Their Composition Ratios , 1982 .

[41]  U. Stimming,et al.  The elctrochemical behaviour of hafnium , 1982 .

[42]  L. Hench,et al.  The effect of environment on silica fracture: Vacuum, carbon monoxide, water and nitrogen , 1998 .