World Abstracts on Microelectronics and Reliability
Transactions on Pans, Hybrids and Packaging. PltP-10, 251 (1974). Results are discussed of an evaluation program for polymer materials considered for applications as protective coatings on hybrid microcircuits. The general organization of the program was in terms of seven potential mechanisms by which coatings could fail to provide protection. Emphasis is on describing those six tests which developed differences in material behavior considered to be significant in terms of the general application. Three involved electrical performance of the films alone or in conjunction with hybrid circuit elements, two dealt with mechanical properties, and one with chemically related behavior. It is suggested that the tests could be used in selecting promising candidates for particular applications which relate to the test conditions or in understanding some failure modes which could be expected in complex hybrid microcircuit assemblies. A brief review is given of those tests which were not considered to develop distinctions between materials. As a point of exception, the role of organic coatings on bare semiconductor device surfaces was not investigated. 9. E L E C T R O N ,
A few examples of applying laser microspectral analysis in semiconductor engineering. GERHARD MOHAPUT and GUDRUN PATZMANN. J E N A Review 4/1974 p. 252. A number of examples demonstrate that the laser microspectral analysis can be employed to advantage for the qualitative local analysis of various materials required in semiconductor engineering. After a thorough examination of the effect of uncontrolled laser pulses on monocrystalline gallium arsenide, a report is given on the determination of silicon in monocrystalline gallium arsenide with the aid of the laser microspectral analysis. For the calibration of the method intended for a local analysis in the range of the trace, a homogeneous silicon dioxide layer on gallium arsenide was employed. The result achieved displayed a detection limit of 2.3 ng silicon. The relative standard deviation in the range from 1 to 50 ng silicon lies at 45%.
Ion implantation boosts threshold of JFET breakdown. Electronics November 28, 1974. p. 39. Ion implantation has been a production tool at most major semiconductor manufacturers' facilities for some years. But only recently has it been applied to j unction field-effect transistors fabricated in a monolithic IC array. That's at National Semiconductor Corp., Santa Clara, Calif., and the results are a seven to eight times boost in the JFET breakdown thresholds over the levels of most other monolithic junction field-effect devices on the market.
Metal-semiconductor contacts prepared by ion implantation. W. ROSINSKI and T. KOMICZ. Electron Tech. 7, (Warsaw). 1/2 1974. p. 13. The paper presents a method of preparing ion implanted contacts to GaAs. The contacts exhibit linear characteristics and low resistivity per square. The results obtained for n- and p-type GaAs are described.
Computer controlled electron-beam projection mask aligner. W. R. LIVESAY. Solid State Tech. July 1974. p. 21. Photolithographic processes in microelectronics have been pushed to their resolution limits and, as a result, new techniques have been proposed both in electron-beam microfabrication and X-ray lithography. However, these new techniques, though demonstrated on an R and D scale, are not readily adaptable to a production process. An electron-beam projection system is described which has been specifically built for production and enables submicron structures to be defined over a large image format (threeinch diameter). The electron projection system described
*Conduction mechanisms in thick f t ~ microcircuit& Semiannual technical report. 1 Jul-31 Dec. 1973. R. W. VEST. Perdue Research Foundation, Lafayette, Ind. 45 (1974). The primary thrust of the experimental program is to relate electrical properties of the thick films to the materials properties and processing conditions through microstructure. The materials properties to be correlated are: resistivity, temperature coefficient of resistivity, coefficient of thermal expansion, interracial energy, particle shape, size and size distribution, and chemical reactivity with other constituents. The processing conditions to be correlated are time, temperature and atmosphere during firing. The specific objectives of the program are to determine the dominant sintering mechanisms responsible for microstructure development and establish the relative importance of the various properties of the ingredient materials, determine the dominant mechanisms limiting electrical charge transport, and establish the relative importance of the various properties of the ingredient materials and develop phenomenological models to interrelate the various materials properties with systems performance. AND
features computer controlled mask-to-wafer alignment and an automatic handling system for 'processing wafers in vacuum.
Electron bombarded semiconductor devices. ARIS SILZARS, DAVID J. BATES and AARON BALLONOFF. Proc. IEEE Vol. 62. No. 8. August 1974. p. 1119. The first electron bombarded semiconductor (EBS) devices have recently appeared on the market. These devices have already demonstrated that EBS has considerable promise as an important new electron device for power amplification and control EBS devices are described with particular emphasis on power devices. The basic EBS principle, some of the analysis used in device design, general considerations in designing the various elements of the device, overall device design, semiconductor processing, and reliability considerations are discussed. Predictions of general directions for future work are made. Some historical information is also presented as well as a brief comparison with other competing power devices.
Electron irradiation damage in silicon containing carbon and diffused ~sO. F. A. ABOU-EL-FOTOUHand R. C. NEWMAN. Solid State Commun. Vol. 15. 1974. p. 1409. Silicon crystals have been diffused with 180, irradiated with 2 MeV electrons at room temperature and then annealed up to 400°C. Infrared absorption measurements of the localized vibrational modes of various defects have been made at each stage.
Laser trimming of thick film resistors. A. F. DYSON and A. J. CABLE. Electrocomponent Science and Technology. 1, p. 51 (1974). Recent papers and conferences have indicated very strongly that thick film screen processing has become a routine production item, with the specifications and economics being considered in detail. The existing resistor and conduction materials and processes have become well documented and are well known on an international scale. This paper reviews the present situation and, in particular, I discusses the effects of a recently-introduced production tool--the laser trimmer.
Ion-implanted semiconductor devices. DON H. LEE and JAMES W. MAYER. Proc. IEEE. 62 (9) September, 1974. p. 1241. Ion implantation is finding increased usage in device fabrication owing to precise control and reproducibility of the charge and depth distribution of the implanted-dopant
World Abstracts on Microelectronics and Reliability
profile. The MOST illustrates the application of charge control through threshold-voltage adjustment and through predeposition for drive-in diffusion to fo~m complementary devices. A compilation of range-energy data for B, P and As in silicon is given along with factors which influence the implanted-dopant distribution after anneal treatments. Implantation procedures are presented for high-frequency bipolar transistors which depend critically on both charge and depth control of the emitter and base profiles. Another important aspect of ion implantation is lateral control, a feature which is necessary for high packing density circuits. Disorder effects associated with implantation through oxide masks are discussed. A brief account of implantation for GaAs devices is also included.
Thermally stimulated current measurements on silicon ]unctions produced by implantation of low energy boron ions. J. C. MULLER, R. STUCK, R. BERGER and P. SIFFERT. Solid State Electron. 1974. Vol. 17 p. 1293. Thermally stimulated current (TSC) measurements have been performed directly on junctions realized by implantation of low energy (15 keV) boron ions into N-type silicon after annealing treatments at different temperatures between 180 and 500°C. The TSC curves have been analysed by a new method based on the measurement of the mean time before re-emission of the trapped carriers and compared with that of Grossweiner. Both methods indicate that the dominant level is a hole trap located at Ev + 0.25 eV. This defect anneals at 260°C and is believed to be correlated with the vacancy-vacancy association. *Some characteristics of ion implanted resistors. K. H. NICHOLAS and R. A. FORD. Mullard Res. Labs UK ( 1973). 4 pp. In 1971 a method was described for making high value resistors for integrated circuits by using implantation damage to reduce mobility. Such resistors have been developed and compact MOS circuits made utilizing them. An investigation to understand more fully the behaviour of damaged layers has been started. A second application of implantation damage is to modify the temperature coefficients of resistance (TCR). A new double-implant technique to control the TCR has been developed and applied to a specific requirement in a bipolar integrated circuit, 1151-2909. Interfacing a source u t i l i ~ g low perveance ion beam extraction to a beam transport system suitable for ion implantation. D. J. T. MAYHALL and W. P. ROBINSON. Solid State Tech. 40 (1974), The feasibility of using a hot filament electron bombardment Penning ion source for yielding substantially higher beam currents (particularly of B +) is investigated. The importance of the extraction system is stressed and a low perveance configuration is described. A higher current source is discussed along with
new equipment required to interface this source with existing implantation equipment. A newly designed quadrupole triplet focussing lens for use with the higher current source is described.
Range and standard deviation of ion-implanted phosphorus and boron in silicon. H. OKABAYASHI and D. SHINODA. NEC Research & Development 35, 10 (1974). The projected range, Rp, and the projected standard deviation, ARp, of 50--260 keV ~lp ions implanted in silicon have been measured by the C - V technique. The measured Rp values satisfy the experimental relation, R, = 1.1 ~m/MeV, reported for higher energy implantation. The measured ARp values at lower energies are larger than the theoretical predictions. The difference shows a tendency to decrease as the ion energy increases and becomes zero at between 200 and 300 keV. The lateral standard deviation, Ay, can also be measured by the C - V technique in combination with the oblique implantation technique. The measured A y values for both 31p and 11B at ion energies studied here are in good agreement with the theoretical predictions. Vacuum systems for ion implantation equipment. J. K. N. SHARMA. Solid St. Tech. 42 (1974). The various types of vacuum systems employed in ion implantation equipment are reviewed. The relative merits of different systems arc discussed and a brief description of a feasible system is given. lonizable materials to produce ions tor implantation. A. AXMAN~. Solid State Tech. 36 (1974). A survey of ion currents obtained during the routine operation of two implanters is presented. The source materials used in a Nielsen and in a hollow cathode source are listed for more than 60 different ion species, including Pd +, IrL Pt* and Au +, which are especially difficult to ionize. Application de la gravure iouique a la microelectronique. A. DUBEI~. Microelectron. & Reliab. 13, 455 (1974). The principles of ion etching are presented and an analysis is made on the effects of the various parameters of this technique on the results obtained. A description is given of a system with a multi beam ion gun which allows areas of 25-30 cm 2 to be processed with a very satisfactory etching uniformity. The energy (1 keV) and current density (1 mA/cm 2) have been chosen to prevent excessive hearings of the substrates processed and to preserve their crystal structure. Various applications of ion etching are described, in particular those concerning masking. Some examples are given showing the advantages of the ion etch technique, particularly for the realisation of microelectronic devices with submicron geometries.