We studied interfacial phase formation between copper and copper-alloy films on SiO2 in order to understand how to improve adhesion. CuCr and CuTi alloy and bilayer films on SiO2 were annealed from 400-600°C for 30 min in an N2 + H2 (5%) ambient. The bilayer systems exhibited refractory metal migration from the interface to the surface where they oxidized. In the CuTi bilayer system, an oxidized interfacial Ti layer was observed. Both CuCr and CuTi alloy systems exhibited refractory metal segregation to the interface and surface. Rutherford backscattering spectrometry and Auger electron spectroscopy were used for elemental depth profiling.

Chemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to “cold flow” and/or “caking” of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness - which itself is dependant upon intrinsic polymer stiffness and cell density.

A simple process for making reliable InP/InGaAs multiple quantum well (MQW) modulator waveguide devices optimized with respect to electro-refractive modulation has been developed. The main concern of this study is the surface properties of the InP surface prior to metallization and etching. A new protective surface passivation technique combining vacuum procurement (∼5xl0-7 Torr) to reduce the water content in the native oxides with an in situ rf-sputter deposition of reactive SiOx onto the surface of InP is reported. This procedure provides smooth surfaces and good optical properties of GaInAs/InP based strip-loaded waveguides.

In this work factors affecting the anisotropy (i.e., difference in vertical and lateral anodization rates) of the aluminum anodization process are investigated. By varying the electrochemical process parameters, a degree of anisotropy of about 0.6 was obtained. The structure of the aluminum porous oxide was determined by a Scanning Electron Microscope. The difference in the anodization conditions for porous aluminum oxide growth along lateral and vertical direction was determined. The developed processing technique was used for forming multilevel VLSI metallization with feature sizes of about 1.2 µm.

A new method is presented to evaluate the resistance to electromigration (EM) of on-chip interconnects. The method is based on high resolution in-situ electrical measurements. In this way, the electrical resistance is measured with high accuracy during electromigration at high temperature. After careful analysis of the isothermal results, it was found that the metallization can be characterized by one parameter: the rate of resistance change (RRC). It is shown that the RRC is very sensistive to the electromigration performance. The performance level of the different metallizations can easily be detected and can be qualified in a quantitative way. The results are also compared with classic Mean Time To Failure (MTTF) results and it is found that there exists an almost linear relationship between the RRC results and the MTTF results. However, the in-situ technique offers the benifit that a metallization can be characterized on a time scale as short as a few days, which is certainly not the case for the classical techniques.

Sputtered Ta36Si14N50 amorphous diffusion barrier layers were reactive ion etched in CF4+02 plasmas. Etch rate varied with gas composition, with 15 percent 02 concentration producing maximum etch rate. Etch rates increased with both pressure and power. Etching proceeded only after an initial delay time which was dependent upon gas composition and applied power. The delay time was probably caused by the presence of a surface native oxide which must first be removed before etching can commence. Auger electron spectroscopy measurements showed the native oxide to be approximately 2 nm thick on as-grown samples, and indicate that near-surface stoichiometry is maintained on etched samples.

WSix films are used extensively for contact, interconnect, and, in some cases, diffusion and Schottky barriers in semiconductor devices1. The electrical and barrier properties of these films are affected by a variety of factors, such as film stoichiometry, morphology, impurities, etc. This paper will address the capabilities and limitations of a variety of techniques which are frequently used to characterize WSix films. Techniques which were studied include: Dynamic and Static Secondary Ion Mass Spectrometry (SIMS), Rutherford Backscattering Spectrometry and Elastic Recoil Detection (RBS/ERD), Auger Electron Spectroscopy (AES), Field Emission Scanning Electron Microscopy (FE-SEM), Total Reflection X-ray Fluorescence (TXRF), Atomic Force Microscopy (AFM), and X-Ray Photoelectron Spectroscopy (XPS). Film characteristics which were studied included surface morphology; grain structure; film stoichiometry; surface and interface oxide thickness and composition; and surface, bulk, and interface impurity concentrations including metallic, atmospheric, and dopant impurities. Cross correlation between the techniques was performed whenever possible in order to compare the relative accuracy of the techniques as well.

Fe-Silicides were formed by annealing MBE-deposited thin Fe layers with a thickness in the range of 24 Å on (7x7) reconstructed Si(l11) substrates. Samples suitable for depth-selective investigations by CEMS (Conversion Electron Mössbauer Spectrometry) were prepared by using only the 57Fe isotope for a few monolayers of the total Fe film, and depositing these selectively right at the interface or separated from it. During the growth the substrate was held at room temperature. The silicide formation upon annealing to temperatures up to 900°C was monitored in situ with RHEED. From the CEMS studies a drastically different sample composition was inferred as a function of monolayer distance from the interface for the as-deposited samples and for annealing temperatures up to 400°C. Analysis of these spectra indicates the presence of metastable and stable iron silicides.

High quality copper thin films have been obtained by low pressure thermally-activated chemical vapour deposition from two different Cu(II) metalorganic precursors, (a) bis(dipivaloyl-methanato) Cu (II) or Cu(dpm)2 and (b) bis(t-butylaceto acetato)Cu(II) or Cu(tbaoac)2, the latter synthesised with a view to reducing the deposition temperature. A comparative study of the volatility and thermal stability of the two precursors, as well as of the growth and microstructure of copper films from these two precursors, is presented.While the threshold deposition temperature is significantly lower for Cu(tbaoac)2 compared to Cu(dpm)2, the growth rate is considerably higher with Cu(dpm)2-Films obtained from Cu(tbaoac)2 are denser and of lower resistivity at a given thickness compared to those from Cu(dpm)2, and are also smoother, exhibiting mirror-like reflectivity.

Thin copper layers were prepared via MOCVD from volatile pyrazolylborato - copper (I) complexes.

Experiments involved chemical vapour deposition in a low pressure reactor between 150 - 350°C in H2/N2/He mixtures were carried out.

Substrate temperature, source temperature and gas composition were varied to obtain the optimum growth rate.

The copper layers were characterized by optical microscopy and scanning electron microscopy, XRD, and WDX. The metallic nature of the deposited films was proved by a four - point - probe measurement of the electrical resistivity.

A selective deposition on metal seeded surface sites was observed on Au, Al, Pt and W vs. Si02- Antiselective deposition was achieved on Pd seeded samples.

The mechanical, thermal, electrical and moisture absorption properties of a series of fluorinated, highly rod-like polyimides and copolyimides are reported. Copolymerization with appropriate flexibilizing comonomers resulted in improved elongations versus those of the highly rod-like homopolymers while maintaining, to a large extent,the other desirable properties of the backbone. These materials are considered prime candidates for interlayer dielectric due to their excellent combination of properties.

We have investigated the microscopic properties of copper and chromium layers deposited on polyphenylquinoxaline (PPQ). PPQ is a thermostable polymer used for multichip module applications. The metal is deposited under ultra-high vacuum conditions and analysed in-situ by X-ray photoemission (XPS) and atomic force microscopy (ex situ). Copper does not react significantly with the PPQ and tends to diffuse into the polymer matrix upon annealing. On the contrary, chromium strongly reacts with the polymer surface at room temperature. With increasing metal coverage, chromium grows in a layer-by-layer mode and the reacted interface is progressively burried under the pure metal layer.

Interfacial chemical bonding states between polyimides (PI) and sputter coated Cr-SiO2 thin film have been investigated mainly by XPS to obtain a reliability basis for thin film resistor application of Cr-SiO2.We tried to leave different level of etch residue by applying two etchants of different etching power, then analyzed the etched surfaces by XPS, TEM and EXAFS. It proved that at first Cr in the sputtered Cr-SiO2 reacts with oxygen atoms which were introduced during O2 plasma treatment of the PI surface and also with original carbonyl oxygen of the PI to offer Cr-O-C bond at the Cr-SiO2/PI interface. This was concluded from the attenuation of Cls peak intensity corresponding to the carbonyl group. Then after thermal annealing, Cr extracted most of the interface oxygen to give a Cr2O3 layer of a discrete thickness. These phenomena were supported by TEM and SR-EXAFS as well.

Residual thermal stresses due to thermal expansion mismatch at dissimilar material interfaces can cause serious problems in the current bonding technology, yet this is an unavoidable consequence as long as the interfaces are fabricated at elevated temperatures. An innovative solution to this problem is that the materials be bonded without applying heat, i.e., bonding at room temperature. A new technique to join two dissimilar materials, “Surface Activated Bonding (SAB)”, has been recently developed. The basic concept underlying this technique is that two atomically clean solid surfaces under contact develop a strong adhesive force. We have recently demonstrated that this method works on various materials systems, including Al2O3, A1N, SiC and Si3N4, on which polycrystalline aluminum is bonded at room temperature. In this paper, we will describe: What is “Surface Activated Bonding”? What are the electronic and chemical driving factors for bonding? Complementary experimental and theoretical studies in elucidating the fundamental aspects of the SAB will be described.

The effect of substrate temperature and process pressure on microstructure of MOCVD-TiN films deposited on oxidized Si substrates are studied by transmission electron microscopy (TEM). It is found that microstructure of MOCVD-TiN films distinctly changes with these deposition parameters and that the resistivity of the films is uniquely related to the microstructure. Films with the lowest resistivity (< 500 μohm-cm) show a uniform semi-columnar grain structure. Films with the highest resistivity (> 10,000 μohm-cm) show a uniform equi-axed micrograin structure. The other films exhibit a bi-layer structure: one layer of semi-columnar grains and the other of equiaxed micrograins. The thickness ratio of these layers changes with the deposition conditions and the resistivity is a unique function of the thickness of the semi-columnar grain layer.

Focused ion beam (FIB) technology is used to modify circuits for early-product design debug; it also has the capability to create probe points to underlying metallurgy, allowing device characterization while maintaining full functionality. These techniques provide critical feedback to designers for rapid verification of proposed design changes.

Current FIB technology has its limitations because of redeposition of sputtered material; this phenomena may induce vertical electrical shorts and limit the achievable aspect ratio of a milled via to 6:1. Therefore, innovative enhancements are required to provide modification capability on planar chip technology which may utilize up to five levels of metallurgy. The ability to achieve high-aspect-ratio milling is required to access underlying circuitry. Vias with aspect ratios of 10:1 are necessary in some cases.

This paper reviews a gas-assisted etching (GAE) process that enhances FIB milling by volatilizing the sputtered material, examines the results obtained from utilizing the GAE process for high-aspect-ratio milling, and discusses selectivity of semiconductor materials (silicon, aluminum, tungsten and silicon dioxide).

Dry etching of common masking materials used in GaAs device technology was examined down to temperatures of −30°C. The etch rates of SiNx, SiO2 and W in SF6/Ar are reduced below 0°C, but the anisotropy of the etching is improved at low temperature. Microwave enhancement of the SF6/Ar discharges produces increases in etch rates of several times at 25°C, but much lower increases at −30°C substrate temperature. The underlying GaAs surface shows increased S and F coverage after low temperature etching, but these species are readily removed either by an ex-situ wet chemical cleaning step or an in-situ H2 plasma exposure. Photoresist etching is less sensitive to temperature and anisotropic profiles are produced between −30 and + 60°C in pure 02 discharges.

The Ga0.51In0.49p/GaAs system has better desired property (ΔEC >ΔEV) than the conventional AlGaAs/GaAs system for heterojunction bipolar transistor (HBT) application. However, in the fabrication of HBTs, a precise control of the etch of the epilayer is very important. In this study, CH4/H2 and BCl3/SF6 were used for the reactive ion etch of the Ga0.51In0.49P/GaAs. It is found that the etch rate of Ga0.51In0.49P could be higher than that of GaAs with CH4/H2 gas mixture under appropriate etching conditions. While in the case of BCl3/SF6, the etching rate of GaAs could be much higher than that of the Ga0.51In0.49P. By properly using CH4/H2 and BCl3/SF6, the fabrication of Ga0.51In0.49P-based device using reactive ion etch could be easily achieved.