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Laser processing of semiconductor silicon. Part II
World Abstracts on Microelectronics and Reliability New thick film multilayer interconnection technology using a N d - Y A G laser. TAKAAKI OHSAKI, ETSUJI SUGITA and SATORU YAMAGUCHI.IEEE Trans. Components Hybrids mf,q Technol. CHMT-5 (4), 382 (1982). The mechanism and capability of the new thick film multilayer interconnection technology using a neodymium-doped yttrium aluminium garnet (Nd-YAG) laser have been theoretically and experimentally described. The mechanism for the conductor pattern formation involves the softening phenomenon of the glass and the thermosetting phenomenon of the organic binder, contained in a thick film conductor paste, by continuouswave (CW) laser beam energy. In the via hole formation, small holes can be drilled by a pulsed laser beam without damage to the under conductor layer, because at constant peak power drilling rate per shot decreases with the increase in depth, that is, with the increase in the number of shots. The conductor size and via hole size formed by the new technology are mainly affected by the laser beam diameter. The minimum beam diameter is limited by the melting phenomenon of a conductor metal for the conductor formation and the substrate tolerance for the via hole formation. Possible conductors and via holes are 25-~tm wide with 10-gm thick gold and 18-gm diameter with 30-gm thick crystallizable glass, respectively.
Major circuit yield improvement: yours for the price of minor resistor redesign. WAYNE JACOBS and THOMAS T. HITCH. IEEE Trans. Components Hybrids mfq Technol. CHMT-5 (4), 388 (1982). A method has been developed to optimize thick film resistor geometries for maximum manufacturing yield by utilizing the mathematics of the normal distribution curve. Use of the method introduces minor changes in resistor geometry to increase the size of the manufacturing window, and thereby to greatly reduce the number of reject circuits. The optimization method is described with examples from an actual redesign of a heart pacer thick film circuit. Sample calculations are made and tables are shown giving complete results for selected resistors. Production yield results are given for the heart pacer circuit. These results show that large yield improvements were in fact achieved on a difficult circuit by use of this optimization method.
Significant features of solder connections to gold-plated thin films. HARRY N. KELLER. IEEE Trans. Components Hybrids m[o Technol. CHMT-5 {4), 408 (19821. An investigation of 60Sn 40Pb solder connections between phosphor-bronze clip-on terminals and Ti-Pd-Cu-Ni-Au and Ti-Pd-Au thin film terminations is described. The investigation consisted of measuring joint strength and analysing resultant fracture interfaces and metallographic cross-sections by scanning electron microscope-energy dispersive X-ray analysis ( S E M EDAX), electron-microprobe (EMP), and X-ray diffraction, both initially and after accelerated temperature aging. Similarities and differences observed for the different terminals and termination conductors used in this, and previous investigations, are presented. Observations are explained by termination interdiffusion, intermetallic compound formation between terminal, termination, and solder constituents, and joint geometry related to the terminal design.
9. E L E C T R O N ,
ION
AND
1003
A ceramic capacitor substrate for high speed switching VLSI chips. DUDLEYA. CHANCE,CHUNG-WEN HO, CHRISTOPHERH. BAJOREKand MICHAELSAMPOGNA.IEEE Trans. Components Hybrids mfq Technol. CHMT-5 (4), 368 (1982). An integrated capacitor substrate which is proposed as an essential part in the realization of a thin film module for high speed digital computing systems is discussed. Several innovative multilayer ceramic (MLC) concepts relative to the fabrication of the desired low inductance capacitor and current paths to chips are described. Ceramic and metal composite material sets which may be used in the fabrication are also proposed. Experimental evaluations of some of the crucial concepts were made and included in the discussions. The result is an elegant approach to the fabrication of one of the key requirements in realizing the thin film high performance module. Specific contact resistance and noise in contacts on thin layers. L. K. J. VANDAMMEand A. DOUIB. Solid-St. Electron. 25 (11 ), 1125 (1982). A method is presented for the calculation of the specific contact resistance and noise of contacts on thin layers. The contribution to the contact resistance and noise of the interface between the contact and the layer is determined from experimental results. Using the developed method on thin CuxS layers with a sheet resistance of 42.5 f~ values for the specific contact resistance of 4 x 10-2f~cm 2 and 2.5 ~ cm2 were observed for two different contact technologies.
LASER
Laser and electron beam scanning of GaAs FETS. W. D. EDWARDS and R. F. HAYTHORNTHWAITE. Microelectron. Reliab. 22 (4), 735 (1982). The results of work to study the effects of laser and electron beam stimulation of GaAs FETs are reported. Studies were made using biassed and unbiassed devices and also using devices with the gate removed by etching. Several mechanisms can be effective but the major cause of the very large induced drain current sensitivities is the photovoltaic effect of the beam on the interface between the semi-insulating substrate and the channel and consequent channel depth changes. A reduction in drain current on illumination observed under negative bias conditions is attributed to the presence of a surface channel on the semiinsulating substrate. The two methods of stimulation produce essentially the same results despite the large differences in charge and input energy. The implications for reliability analysis are discussed. Laser processing cuts wider swath. NORMAN ALSTER. Electronics, 106 (15 December 1982). New applications in semiconductor processing and microanalysis developed in the past few years excite seminar at materials meeting. Laser processing of semiconductor silicon. Part II. THOMASJ. MAGEE and T. KEITH MCNA8. Solid St. Technol., 101
BEAM
TECHNIQUES
(December 1982). An experimental study to compare and contrast the Q-switched alexandrite laser with a frequency doubled Q-switched N d : Y A G laser and a scanning cw argon ion laser for the annealing of ion implantation damage in silicon was performed. High dose implants of arsenic and phosphorus were annealed and then analysed using several physical and electrical techniques. The alexandrite laser was found to anneal the implanted layer and activate the dopants as effectively as the other two laser systems. In Part II, an experiment is described in which a Q-switched alexandrite laser was used to dope silicon with phosphorus to concentrations greater than 1 x 102°cm-3. Here the silicon wafer was immersed in a low pressure phosphine environment and then laser irradiated to produce solar cell material. In a third study a Q-switched alexandrite laser was used to getter the back surface of (100) orientation silicon wafers. Using appropriate optics to produce a line profile, the wafers were rear surface irradiated and then oxidation-induced stacking fault densities were measured. Significant reductions (up to 80 %) were obtained on the irradiated portions of the treated wafers. Optical emission and pressure correlations during plasma etching. E. S. BULAT, G. F. DOYLE and B. GELERNT. Semiconductor Int., 113 (November 1982). Good correlation of
Major circuit yield improvement: yours for the price of minor resistor redesign. WAYNE JACOBS and THOMAS T. HITCH. IEEE Trans. Components Hybrids mfq Technol. CHMT-5 (4), 388 (1982). A method has been developed to optimize thick film resistor geometries for maximum manufacturing yield by utilizing the mathematics of the normal distribution curve. Use of the method introduces minor changes in resistor geometry to increase the size of the manufacturing window, and thereby to greatly reduce the number of reject circuits. The optimization method is described with examples from an actual redesign of a heart pacer thick film circuit. Sample calculations are made and tables are shown giving complete results for selected resistors. Production yield results are given for the heart pacer circuit. These results show that large yield improvements were in fact achieved on a difficult circuit by use of this optimization method.
Significant features of solder connections to gold-plated thin films. HARRY N. KELLER. IEEE Trans. Components Hybrids m[o Technol. CHMT-5 {4), 408 (19821. An investigation of 60Sn 40Pb solder connections between phosphor-bronze clip-on terminals and Ti-Pd-Cu-Ni-Au and Ti-Pd-Au thin film terminations is described. The investigation consisted of measuring joint strength and analysing resultant fracture interfaces and metallographic cross-sections by scanning electron microscope-energy dispersive X-ray analysis ( S E M EDAX), electron-microprobe (EMP), and X-ray diffraction, both initially and after accelerated temperature aging. Similarities and differences observed for the different terminals and termination conductors used in this, and previous investigations, are presented. Observations are explained by termination interdiffusion, intermetallic compound formation between terminal, termination, and solder constituents, and joint geometry related to the terminal design.
9. E L E C T R O N ,
ION
AND
1003
A ceramic capacitor substrate for high speed switching VLSI chips. DUDLEYA. CHANCE,CHUNG-WEN HO, CHRISTOPHERH. BAJOREKand MICHAELSAMPOGNA.IEEE Trans. Components Hybrids mfq Technol. CHMT-5 (4), 368 (1982). An integrated capacitor substrate which is proposed as an essential part in the realization of a thin film module for high speed digital computing systems is discussed. Several innovative multilayer ceramic (MLC) concepts relative to the fabrication of the desired low inductance capacitor and current paths to chips are described. Ceramic and metal composite material sets which may be used in the fabrication are also proposed. Experimental evaluations of some of the crucial concepts were made and included in the discussions. The result is an elegant approach to the fabrication of one of the key requirements in realizing the thin film high performance module. Specific contact resistance and noise in contacts on thin layers. L. K. J. VANDAMMEand A. DOUIB. Solid-St. Electron. 25 (11 ), 1125 (1982). A method is presented for the calculation of the specific contact resistance and noise of contacts on thin layers. The contribution to the contact resistance and noise of the interface between the contact and the layer is determined from experimental results. Using the developed method on thin CuxS layers with a sheet resistance of 42.5 f~ values for the specific contact resistance of 4 x 10-2f~cm 2 and 2.5 ~ cm2 were observed for two different contact technologies.
LASER
Laser and electron beam scanning of GaAs FETS. W. D. EDWARDS and R. F. HAYTHORNTHWAITE. Microelectron. Reliab. 22 (4), 735 (1982). The results of work to study the effects of laser and electron beam stimulation of GaAs FETs are reported. Studies were made using biassed and unbiassed devices and also using devices with the gate removed by etching. Several mechanisms can be effective but the major cause of the very large induced drain current sensitivities is the photovoltaic effect of the beam on the interface between the semi-insulating substrate and the channel and consequent channel depth changes. A reduction in drain current on illumination observed under negative bias conditions is attributed to the presence of a surface channel on the semiinsulating substrate. The two methods of stimulation produce essentially the same results despite the large differences in charge and input energy. The implications for reliability analysis are discussed. Laser processing cuts wider swath. NORMAN ALSTER. Electronics, 106 (15 December 1982). New applications in semiconductor processing and microanalysis developed in the past few years excite seminar at materials meeting. Laser processing of semiconductor silicon. Part II. THOMASJ. MAGEE and T. KEITH MCNA8. Solid St. Technol., 101
BEAM
TECHNIQUES
(December 1982). An experimental study to compare and contrast the Q-switched alexandrite laser with a frequency doubled Q-switched N d : Y A G laser and a scanning cw argon ion laser for the annealing of ion implantation damage in silicon was performed. High dose implants of arsenic and phosphorus were annealed and then analysed using several physical and electrical techniques. The alexandrite laser was found to anneal the implanted layer and activate the dopants as effectively as the other two laser systems. In Part II, an experiment is described in which a Q-switched alexandrite laser was used to dope silicon with phosphorus to concentrations greater than 1 x 102°cm-3. Here the silicon wafer was immersed in a low pressure phosphine environment and then laser irradiated to produce solar cell material. In a third study a Q-switched alexandrite laser was used to getter the back surface of (100) orientation silicon wafers. Using appropriate optics to produce a line profile, the wafers were rear surface irradiated and then oxidation-induced stacking fault densities were measured. Significant reductions (up to 80 %) were obtained on the irradiated portions of the treated wafers. Optical emission and pressure correlations during plasma etching. E. S. BULAT, G. F. DOYLE and B. GELERNT. Semiconductor Int., 113 (November 1982). Good correlation of