Dielectric Etch Research Articles

Reduction of Sidewall Roughness During Dry Etching of SiO2

The appearance of striations on dry etched semiconductor laser mesas is a common feature of these structures. We describe a number of different methods of reducing the extent of this roughness, including the choice of dielectric etch chemistry, modification of the initial resist processing and deposition of a SiN sidewall to prevent additional rougheningduring the plasma etch step. SF6 is found to be preferable to CF4 for dielectric etching because of an absence of polymer formation. This produces smoother SiO2 sidewalls. Flood exposure of the initial photoresist mask and optimization of the postbake temperature also produces smoomer sidewalls on the subsequently etched SiO2. The sidewall can also be protected from roughening that occurs during the dry etch step by coating it with a low temperature SiN layer. A combination of all of these methods produces sidewalls with morphological variations of ≤500Å.

Dry etching of TiN/Al(Cu)/Si for very large scale integrated local interconnections

Patterning Ti/TiN/Ti/Al(2 wt. % Cu)/Si interconnection lines over 700 nm topographic steps in SiO2 with an angle of 84° is reported using a reactive ion etching. The etching gas is a mixture of BCl3/Cl2/N2/CHCl3 and the etching process uses a combination of high and low reactor pressures in a single wafer etching tool. No metal rails along the sidewall of topographic features were detected using an electrical test site. The etched metal profile shows a near vertical metal sidewall with negligible undercut. The metal linewidths are 0.7 to 1.8 μm wide with the variation of about 0.1 μm near the steps, due to resist linewidth variations over the topographic step. It also demonstrated that the Al(Cu) line can be a good landing pad for contact hole dielectric etching.

Fabrication Technologies for III-V Compound Semiconductor Photonic and Electronic Devices

This paper describes process technologies for fabricating III-V photonic and high-speed electronic devices. The major processes involved are contact metallization, dielectric film deposition, wet and dry etching, diffusion, implantation, photolithography, wafer separation, and die bonding. For the photonic devices, the emphasis is on those long-wavelength devices that are fabricated with the InP/InGaAsP material system. In contrast, for the high-speed electronic devices, we discuss the fabrication of field-effect transistors with the GaAs/AlGaAs system. We present representative examples in detail and, where possible, identify commonalities and contrasts in their processing and in the process criticality. We review specific constraints that determine the processing technique, and give examples of how processing influences device performance and reliability. Finally, we assess the current trends in process development that are relevant to III-V device fabrication.

Laser-enhanced patterning using photothermal effects: maskless plating and etching

We review our work on laser-enhanced plating and etching with emphasis on the chemical, electrochemical, and thermal mechanisms giving rise to the experimental observations. The metallurgical properties of the deposits and their applications, particularly in the field of microelectronics, are also discussed. The work on laser-enhanced electroplating and electrodeless plating includes high-speed deposition of copper, gold, and nickel by using the argon-ion laser as the source of localized energy. Deposition rates up to 3 orders of magnitude higher have been observed for laser-irradiated regions compared with nonirradiated ones. Mechanisms responsible for the plating enhancement are (1) enhanced chemical and electrochemical kinetics with increased temperature, (2) shifts in the local rest potential with temperature, and (3) local agitation of the solution as a result of large temperature gradients. Applications of these techniques to circuit design and repair as well as to high-speed plating of precious metals onto electrical contact areas of microelectronic circuits are considered. Experiments on high-speed laser-enhanced etching of several dielectrics are also reviewed. Volume removal rates as high as 106μm3/sec for an alumina/TiC ceramic and 105μm3/sec for 〈111〉 silicon using KOH as the etchant have been obtained.

Endpoint detection in plasma etching

Plasma etching is a main stream technology in integrated circuit fabrication. The general trend towards fine linewidths and decreasing thickness of underlying layers (etch stops) results in an increasing dependence on highly controlled plasma etch processes. Such tight control requires in situ process monitoring, particularly, for determination of the etch endpoint. This paper reviews the various methods for endpoint detection. A novel application of interferometric principles for very precise etch endpoint determination in high density circuits is described. A comparison of several methods used simultaneously in a plasma planarization process is presented. The etch endpoint can also be determined by monitoring the pressure change in the chamber upon completion of the etch. An application of this method to dielectric etching is demonstrated.

Profile of trapped charge in silicon nitride films in MNOS structures

The relaxation current in the system electrolyte-dielectric-semiconductor is measured in the process of dielectric etching. A theoretic calculation of the charge profile in the MNOS structure dielectric is conducted for non-uniform distribution of trapping centres and charge injection from a field electrode. The distribution of trap density through the nitride film and their trapping cross-section are determined. The height of the triangular barrier for the electrons at the boundary nitride-aluminium is estimated. An effect enhancing the hole injection from a field electrode due to illumination is discovered. [Russian Text Ignored].

Summary Abstract: The formation and decomposition of methanol on Ru(001) studied by EELS, TDMS, and work function measurement

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Mechanisms of Plasma‐Enhanced Silicon Nitride Deposition Using SiH4 / N 2 Mixture

The mechanism of plasma‐enhanced vapor deposition of silicon nitride is studied by varying process parameters, such as substrate temperature, rf power, reactant gas ratio, and total pressure. The film composition (Si, N, O, and H) is determined by electron microprobe and infrared analysis. From these analyses, it is established that the film composition is determined not only by the reactant gas ratio, but also by a combined function of the rf power and total pressure in terms of , with a system‐dependent factor. The dependence of film composition on can be related to the radical generation processes. The substrate temperature is found to affect the film composition as well. Greater substrate temperature produces films with less hydrogen and more nitrogen, and hence, higher density. The film dielectric property and plasma etching rate are both studied and found to be dependent on the film composition. Finally, a three‐step deposition mechanism, namely, radical generation, radical adsorption, and adatom rearrangement, is proposed to explain the reaction scheme, and an ion incorporation mechanism is proposed to explain the change of film physical properties.

An Integrated Microstrip Circulator (Correspondence)

Ferrite circulators, incorporated as integral parts of a microstrip circuit on a copper-clad dielectric substrate, have been developed and tested. These circulators do not require the machining of a hole in the dielectric substrate or etching of the ferrite metalization. 20-dB isolation bandwidths of 3.5 to 4 percent in the frequency range 1.75 to 2.23 GHz were measured.

Reactively Sputtered Silicon Oxynitride as a Dielectric Material for Metal‐Insulator‐Metal Capacitors

Silicon oxynitride was formed by rf reactive sputtering of silicon in mixtures of . The dependence of dielectric constant, etch rate, breakdown strength, and IR transmittance on the concentration in the plasma was determined. Five to ten per cent gave an average breakdown strength of for metal‐insulator‐metal capacitors having molybdenum electrodes. The other capacitor parameters were also measured. An explanation of the high breakdown strengths in these capacitors is suggested.

Silicon Nitride Films by Reactive Sputtering

Silicon nitride films (from 500 to 7500Aå in thickness) have been deposited on silicon and silicon dioxide by reactive sputtering of a silicon cathode in a N2 glow discharge. Both d‐c and rf sputtering have been investigated. Physical and chemical properties of silicon nitride films prepared by sputtering were examined in reference to the process variables. The rate of deposition was approximately proportional to the square root of rf power density. Film density increased with power density, and decreased with gas pressure. Optimum gas pressure was in the range . Higher pressures resulted in less dense and electronically leaky films. Dielectric constant and etch rate in HF solution appeared to correlate well with film density. Residual pressure higher than was found to have a most detrimental effect. Argon and nitrogen gas mixtures resulted in excess silicon incorporation in the deposited nitride films.