Dielectric Passivation Layer Research Articles

THERMAL CHARACTERIZATION OF IC PASSIVATION LAYERS USING JOULE HEATING AND OPTICAL THERMOMETRY

The temperature rise in microdevices is in many cases strongly increased by the thermal resistance of dielectric passivation layers. This problem is especially important for integrated circuits (ICs) containing novel low-dielectric-constant passivation, such as polymers and porous oxides. We report progress on developing a technique for measuring the thermal properties of these passive layers, which uses harmonic Joule heating in a metal line and compares solutions to the heat equation with a photothermal signal. This approach makes measurements possible over a wide range of heating frequencies and allows the thermal conductivity to be determined without calibration or precise knowledge of the heat capacity of the layer. Data are reported for the thermal conductivity of thermally grown silicon dioxide and polymer thin films.

Use of a Native Oxide of AlxGa1−xAs in the Fabrication of Integrated Laser/Modulators

ABSTRACTA planar self-aligned process for fabricating integrated lasers and modulators is described. This process employs a native oxide of AlxGa1−xAs to form the waveguide structure and dielectric passivation layer. Wet oxidation of AlxGa1−xAs is being investigated to determine possible processing parameters that result in good quality oxides and a reliable fabrication process. Variations in the mechanical properties were observed with changes in processing parameters.

Atomic Layer Controlled Deposition of Al2O3 Films Employing Trimethylaluminum (TMA) and H2O Vapor

AbstractSequential surface chemical reactions for the controlled deposition of Al2O3 films were studied using transmission Fourier transform infrared spectroscopy (FTIR). Experiments were performed in situ in an ultrahigh vacuum UHV chamber using high surface area alumina membranes. Trimethylaluminum [Al(CH3)3] (TMA) and H2O vapor were employed sequentially in an ABAB... binary fashion to achieve atomic layer controlled growth. An optimal Al2O3 growth procedure was established that employed TMA/H2O exposures at .3 Torr and 500 K. The experiments revealed that each reaction was self-terminating and atomic layer controlled growth was dictated by the surface chemistry. The controlled deposition of Al2O3 may be employed on silicon surfaces for the formation of high dielectric gate and passivation layers.

High resistivity AlO x thin films deposited by a novel two-step sputtering process

A novel sputter deposition technique has been developed in which the first layer and the second layer are controlled independently. This technique has been used to prepare AlO x thin films as dielectric passivation layers. A very thin film is deposited first with the substrate not exposed to the plasma region, while the remaining part is deposited in the plasma region. This new technique produces high resistivity AlO x films 500 nm thick of wide area, even on rough substrate surfaces. This result indicates that it is necessary to optimize the energy and flux of bombarding ions or neutral atoms in the first-layer formation and in the second-layer formation independently for densification of the films. The applicability of this approach could be extended to the deposition of other materials.

Advanced Dielectrics for Passivation of INSB

ABSTRACTA combination of Electron Cyclotron Resonance (ECR) plasma, electrochemical, and chemical growth process were examined to synthesize dielectric surface passivation layers on InSb. The material properties of ECR-grown SiOxNyon InSb at temperatures from 30°C to 250°C were investigated. Composition analysis was done using Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD). The electrical quality of the passivation layer was characterized with capacitance-voltage (C-V) measurements on metal-insulator-semiconductor structures over the frequency range from 1 kHz to 1 MHz. Sulfided layers, Si3ON2on InSb, and sulfided layers capped with S3ON2all exhibited good C-V properties consistent with interface state densities on the order of 1011/cm2-eV, and flatband voltages of magnitude less than 1 V. The difference in adhesion of Si3N4on InSb and the adhesion of Si3ON2on InSb was described in terms of the strength of the bonding at the dielectric-InSb interface. This work is the first to demonstrate passivation of an InSb surface with high-quality ECR silicon oxynitrides grown at room temperature.

Electron beam testing of multilevel metal integrated circuits

Fundamentally, voltage contrast is a well established technique for determination of voltages on metal surface which can be directly probed with an electron beam. However, actual integrated circuits (IC) consist of two or more conducting layers (metal and doped polysilicon) separated by dielectrics and covered by a dielectric passivation layer. Our work has addressed: i) the removal of dielectric layers (depassivation) by reactive ion etching (RIE) or selectively by focused ion beam etching to allow access to exposed metal lines; ii) modelling effort to understand how the materials and geometric parameters of multilevel IC's affect voltage contrast measurements, and iii) improvements in retarding field spectrometer based measurement techniques.

Sequential surface chemical reaction limited growth of high quality Al2O3 dielectrics

Sequential surface reactions of trimethylaluminum and water vapor have been used to deposit Al2O3 on Si(100) surfaces. The self-limiting nature of the surface reactions allows precise control of the thickness of the deposited layers and gives rise to films with highly conformal step coverage. High quality dielectrics have been deposited at temperatures as low as 100 °C. Resistivities of 1017 Ω cm, breakdown strengths of 8×106 V/cm, and interface-state densities of 1011 states/eV cm2 have already been achieved and they suggest possible applications as a gate insulator or a dielectric passivation layer.

Corrosion of Aluminum Interconnect Passivated with Polyimide or Silicon Nitride

Polyimides have been considered the most promising organic polymers for use as an inner-layer dielectric or over-metal passivation layer on ICs. These polymers have certain processing advantages over traditional inorganic dielectrics such as SiO2 or Si3N4. However, polyimide (PI) must meet the stringent standards that inorganic materials have met, including good adhesion to the substrate and resistance to diffusion of water. Failure to meet these standards may result in increased aluminum corrosion rate and consequent degraded reliability.

Corrosion of Aluminum Interconnect Passivated with Polyimide or Silicon Nitride

Polyimides have been considered the most promising organic polymers for use as an inner-layer dielectric or over-metal passivation layer on ICs. These polymers have certain processing advantages over traditional inorganic dielectrics such as SiO2 or Si3N4. However, polyimide (PI) must meet the stringent standards that inorganic materials have met, including good adhesion to the substrate and resistance to diffusion of water. Failure to meet these standards may result in increased aluminum corrosion rate and consequent degraded reliability.In this study, the corrosion rate of sputtered aluminum test patterns passivated with either PI or plasma-deposited silicon nitride (SiN) was measured at 85°C and 85% relative humidity (RH). The objectives of this work were to: (1) assess the failure rates of biased aluminum interconnection with PI or SiN passivation; (2) determine the failure mechanisms in each case; and (3), as a result, evaluate the suitability of PI passivation for high voltage ICs in non-hermetic packages. In this report, the test device fabrication and evaluation procedures are first described. Then the results are presented, including both the failure rate measurements and the failure analyses. Finally, the results are compared and discussed.

Materials for magneto-optic data storage (invited) (abstract)

The optimization of magneto-optic media for data storage applications involves a detailed consideration of the impact of material properties on the overall performance and reliability characteristics of the complete media design, which includes both the active layer structure and the substrate material. Currently, the most highly developed materials for the active layer are the amorphous rare earth-transition metal (RE-TM) alloys. The RE-TM composition determines both the Curie temperature and the compensation temperature, both of which parameters affect the sensitivity, and therefore the data rate which can be achieved using currently available diode lasers. The thermal and optical characteristics of the active layer thin-film structure affect the sensitivity, and also determine the degree of enhancement of the shot-noise-limited SNR during playback. Reliability of magneto-optic media is affected by uniform surface oxidation of RE-TM alloys, which leads to reduced Kerr rotation through the formation of an absorptive surface layer with only in-plane anisotropy. The proper choice of dielectric passivation layers and deposition process can significantly limit this and other degradation mechanisms. The choice of substrate material must be compatible with the coating process for the active layer structure, provide a stable mechanical interface to the drive mechanisms, and also possess good optical properties, most notably low birefringence. This talk will review the current directions in materials research on magneto-optic media, and relate the physical characteristics of the materials involved to the major requirements of the data storage application.

Micromethod for Refractive Index Determination of Thin Films Using Liquid Standards

Refinements, simplifications, and a change of perspective are reported for determining the refractive index of thin transparent films by the liquid‐matching method initially described by Lewis. The procedure requires establishing a median value between two observed refractive index end points by microscopically monitoring the white‐light intensity on each side of a film step. Although applicable to thin films whose refractive indexes range from 1.4 to 2.1, results are predominantly based on observations made with thermally grown and plasma‐deposited silicon nitride films. The technique has been applied successfully to in situ determinations of refractive indexes of dielectric passivation layers over single integrated‐circuit pellets.

Advances in deposition processes for passivation films

A review is presented of deposition processes for forming dielectric passivation layers on silicon semiconductor devices, with emphasis on recent advances in this field. Materials of prime interest are thin-film dielectrics used as secondary passivants deposited by several types of chemical vapor deposition (CVD) processes. The fundamental principles, deposition parameters, advantages, applicability, and limitations of the various types of CVD for dielectric passivation films are described and compared. The CVD processes discussed include low- and high-temperature CVD at normal pressure, and the relatively new technologies about to emerge for large-scale applications−low-pressure CVD at low and high temperatures, and plasma-enhanced CVD.