ISSN:0022-5355    

DOI:10.1116/1.568627

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

A discussion of the difficulties of measuring adhesion. Results obtained by various methods are critically considered in the light of theoretical and other estimates of the magnitude to be expected. New ideas on scratch testing are presented and some of the difficulties associated with this method are discussed. For measuring the adhesion of thin films, it still remains as one of the most successful methods and some of the more recent results obtained in this way are presented. In the case of metal films on polymer surfaces, there is increasing evidence of charge transfer across the interface and electrostatic bonding may make a significant contribution to the measured adhesion.

ISSN:0022-5355    

DOI:10.1116/1.568754

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

Thin film interconnection metallization and passive thin film components of semiconductor devices are subject to four primary modes of failure. They are (i) metallurgical reactions, (ii) electro chemical corrosion, (iii) electromigration, (iv) process related imperfections.The use of alternative metallization systems for the commonly used aluminum is desirable for devices operating at high−current densities or in nonhermetic applications. If these alternate metallization systems consist of more than one material, then not only must the metallurgical stability between the metallization and the silicon be investigated, but also the effect of interdiffusion of the film constituents themselves. Such investigations conducted on an extensive combination of materials show that gold combined with tungsten as a barrier and with titanium as an adhesive produces excellent results with respect to processing and operation on complex integrated circuits and microwave power transistors.Conductors and passive components on semiconductor devices are subject to electrochemical corrosion if moisture is present on the surface of the device. Tests made under conditions of temperature, humidity, and electrical bias are used to determine the stability of device metallization for nonhermetic applications. Electrochemical corrosion, under these conditions, is a rapid mode of device failure because of the close proximity and minuteness of the conductor lines or passive components. Passivation with deposited glass films afford some degree of protection to the device but exposed wire bonding pads, pinholes, and cracks in the glass and glass composition significantly affect the degree of passivation afforded by these films.The complexity of integrated circuits in system function and in component parts is ever increasing. However, because of yield and assembly limitations such complexity cannot be paralleled with a corresponding increase in die size. As a result, conductors are being reduced in size, are required to operate at higher temperatures, and at current densities exceeding 106A/cm2. The result of these stresses is to accelerate the migration of the metallic films with the consequent formation of voids and hillocks in the conductor metallization. Micrographs taken with the scanning electron microscope, both in still and motion form, show that the voids reduce the cross sectional area of conductors, contributing to conductor burn out, and the hillocks grow outward from the film surface which could ultimately cause shorts even through overlying dielectric layers. This migration of metal atoms is largely along grain boundaries and effective methods of inhibitions are (a) use of a metallization material with the smallest self−diffusion coefficient, (b) use a large grain size film structure and, (c) the addition of impurities to the film to reduce the grain boundary effect. Process−related failure mechanisms extend from an over−etch condition to inadequate process control, through poor film adhesion, to excessive thinning or discontinuities in the film because of inadequate coverage over the surface of the substrate. This latter factor is the primary concern of the thin film technologist, in that adequate conductor film continuity must be maintained over a surface which is severely contoured by prior etching of the silicon and overlying dielectric and metal films. Since these steps cannot be eliminated nor even reliability tapered for best film coverage, it is necessary to compensate for this by employing special procedures during the film deposition.Elevated substrate temperature, along with appropriate substrate nutation, can enhance the step coverage of aluminum films. However, for refractory metals, or if high−substrate temperature would be detrimental to device performance, deposition by the appropriate mode of sputtering can be used to an advantage.SEM micrographs are useful in demonstrating the results of a particular process, and along with appropriate temperature stress testing, are used to define the conditions for a successful metallization system and film depostion procedures.

ISSN:0022-5355    

DOI:10.1116/1.568760

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

The introduction of semiconductor techniques and integrated circuits on silicon chips has stimulated a need for denser and smaller interconnection methods. This need has been met using the now common hybrid technologies of providing thin film conductors, resistors, and possibly capacitors on ceramic substrates with subsequent addition of applique devices. The thin film techniques and properties are well documented in the literature.1,2The thin film technology was chosen by Sandia in 1970 for use in high−reliability microcircuits. The basis of specific technologies selected and early production results have been described by Tapp and Wiley.3One set of technologies was chosen for detailed development studies; this set included alumina substrates with sputtered tantalum nitrate resistors and evaporated chromium−gold conductors.The basis for selection of a metallization system for production processing and the tribulations of instituting that system in a production line are briefly reviewed. The use of surface analytical techniques and complete R and D investigations for assuring good product are important for successful commercial processing of thin films. The success is evident in current production where the yield of the chromium−gold evaporation processing is 98% and of the subsequent thermocompression gold−gold bonding is 96%.3The chromium−gold evaporated metallization of 3 μ Au on 3 nm Cr on 99.5% alumina substrates provides a good conductor with resistivities from 3.0 to 4.0μΩ−cm. The major limitation of the system is diffusion of chromium to the Au surface. Deposition at elevated substrate temperatures of 300−400°C provides larger gold grains and appears to place the chromium in solution, minimizing the rapid grain boundary or surface diffusion.

ISSN:0022-5355    

DOI:10.1116/1.568763

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

In the course of developing techniques for ion−beam etching of solid bulk materials and thin deposited films, we undertook a systematic investigation of etch rates of several materials and the dependence of etch rate on beam parameters and beam angle of incidence. Results of these measurements are presented. Under certain conditions, cones formed on the surface being etched. An explanation for this instability phenomenon is given. In most practical applications of ion−beam etching, suitable masking techniques are necessary. We have developed procedures for photoresist masking for two classes of etching: (a) high−resolution, shallow−depth etching (typical dimension ∠1 μ); (b) low−resolution, very deep etching (typical dimension ∠50 μ). The methods used will be discussed, and in particular we will consider the influence of redeposition of sputtered material and the profile of the photoresist on the final−etched wall shape.

ISSN:0022-5355    

DOI:10.1116/1.568767

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

This paper will review the major bonding and interconnection methods being employed in microelectronic manufacturing. Although there is a large number of variations of method, the physical processes for achieving a reliable interconnection can be reduced to two categories: solid phase joining and liquid phase joining. Solid phase joining is achieved as the name implies, without melting by the formation of regions of intimate metal−to−metal contact utilizing the application of energy. The two principle sources of energy are a combination of heat and pressure (thermocompression) and ultrasonic vibrations, and excellent papers have been written describing the physical processes occurring at the interface in each of these processes.1,2Liquid phase joining is achieved by following a thin layer of nonferrous filler metal between the surfaces to be joined, and the physical processes of the wetting of the joint surfaces have been described in detail.3By far the most widely used method for making interconnections in microelectronics involves soldering the semiconductor die to the header and joining individual areas of the circuit to the package leads using fine diameter wires. The die bond is generally achieved with high−strength gold−based eutectic solders; however, with increasing die size, the stresses due to thermal expansion mismatch increase until it becomes necessary to use low−strength, highly plastic lead−based solders in place of the gold solders to prevent the die from cracking.4The wire bonds are achieved utilizing either thermocompression or ultrasonic bonding, and excellent reviews have been written summarizing the methods for manufacturing the wire bonds and for testing and evaluating their integrity.5,6The major advantages of the die and wire bond interconnection system are its flexibility and simplicity, while its disadvantages relate to the high−labor dependence of the system both in terms of cost and reliability.Another interconnection method utilized where long−term reliability is required is beam lead bonding. In this technique, gold beams are formed leading from the device metallization, generally by plating, and thermocompression bonding is used to form the joint with the metallized substrate.7More reliable (at high temperatures and current densities) multimetal gold systems8are used for the device metallization and special dielectrics for passivation, and the advantage of the over−all system is increased reliability particularly under harsh operating conditions. The disadvantages are increased cost (due to the extra processing steps involved), and lack of general availability. A third interconnection method involves creating bumps on the semiconductor device surface, flipping the chip, and simultaneously joining these bumps to the substrate. The most common method of joining employs lead−based soft solders,9although thermocompression and ultrasonic bonding systems have also been employed in a number of development schemes. Recent emphasis has been on automating bump interconnection systems utilizing film carrier techniques.10The advantages of the system involve potential lower costs for packages involving many bonds and the excellent reliability reported for solder joint system.11The disadvantages include the complex metallurgy system required and the lack of inspectability.A fourth interconnection method is spider bonding employing ultrasonic bonding to join a standard aluminum metallized die to an etched or stamped aluminum ’’spider’’ which in turn is welded to a lead frame.12The advantages of this method include the potential lower costs due to simultaneous bonding, and the simple metallurgy system. The disadvantages include lack of availability and the requirement for an additional joint.

ISSN:0022-5355    

DOI:10.1116/1.568793

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

An impact−ionization model predicts a negative resistance type of dielectric instability and breakdown in wide bandgap insulators. The instability develops by the injection of electrons from the cathode, impact ionization of the lattice, and a distortion of the electric field which leads to a further increase in impact ionization. For the case of thin films, it is necessary to invoke a nonlocal ionization rate in order to obtain a negative resistance instability. O’Dwyer’s avalanche theory of breakdown, which applies well to semiconductors, cannot be used to predict a negative resistance in the small multiplication limit appropriate to wide bandgap insulators. The impact−ionization model presented here depends upon two critical parameters: the ionization bandgap of the material and the electron−LO phonon scattering length. Evaluated for the exemplary case of SiO2, the model predicts a current density and an average field at breakdown which increase rapidly for film thickness below 200 Å.

ISSN:0022-5355    

DOI:10.1116/1.568797

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

The resistance of a ZnO thin film deposited by rf sputtering exhibits a change of 2 1/2−5 orders of magnitude as the ambient gas is cycled from nitrogen to oxygen. Hall measurements imply that the sputtered films aren−type semiconductor and that the resistance increase caused by oxygen adsorption is related to the decrease of carrier density of the sample. Sample resistivity is found to change with thickness; in oxygen, it decreases as thickness increases, but in a vacuum, it increases as thickness increases. The response time for resistance changes vs environmental changes depends highly on the sample temperature; it is slow at room temperature, but a rapid response can be seen at temperatures higher then 365°C.

ISSN:0022-5355    

DOI:10.1116/1.568567

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

It is shown that amorphous Nb2O5films 2400 Å thick produced by anodization can be doped with Nb by rf sputtering of Nb atoms at substrate temperatures of 150°C. Large increases in electrical conductivity, reductions in thermal activation energy, and increases in capacitance as function of sputtering voltage in the range 2−5 kV support this interpretation. The high−field conduction process also changes from the Poole−Frankel mechanism often found in insulating films, where the conductanceG=G0exp(KV1/2) to the Poole mechanism whereG=G0exp(KV) found in Nb doped films. The doping concentration for 2400−Å films was calculated using the experimental values of the exponentKand found to be 1019atoms/cm3for films sputtered with Nb at an rf voltage of 3 kV. Capacitance variation as a function of voltage and temperature also support these conclusions. These effects are interpreted on the basis of possible implantation and temperature−aided diffusion process.

ISSN:0022-5355    

DOI:10.1116/1.568582

出版商:American Vacuum Society    

年代:1975

数据来源: AIP

摘要:

The characteristics of current flow through thermally and anodically grown oxides of vapor deposited and bulk InSb are reported. The magnitude of the current though the thermal and anodic oxides are found to be markedly different. The thermally grown oxides have very low resistance similar to In2O3. The anodic oxides are insulating and the current flow is characteristic of Schottky emission. The anodic oxides grown on bulk single crystals (BSC) and on thin films deposited at 150° and 350°C have essentially the same current−voltage characteristics. The breakdown strength of the BSC oxides is approximately 50% greater than of the thin film oxides.

ISSN:0022-5355    

DOI:10.1116/1.568612

出版商:American Vacuum Society    

年代:1975

数据来源: AIP