摘要:

The energy distribution of electrons emitted from an Al/Al2O3/Au metal–insulator–metal (MIM) electron emitter is measured. The thickness of the insulator is 5.5 nm. The energy distribution becomes narrower as the operating voltageVddecreases since the low energy tail of the distribution is cut off by the potential barrier of the surface work function φ of the emitter. When the emitter is operated in the nonformed state, ΔE, the full width at half‐maximum of the distribution, is 0.32 eV forVd=5.0 V, which is slightly above φ of Au (4.7 eV). AsVdincreases, the high‐energy tail of the distribution broadens whereas the shape of the low‐energy tail remains unchanged. For a formed MIM emitter, ΔEbecomes broader by 0.15–0.2 eV more than ΔEof a nonformed emitter at eachVd; thus, operation in the nonformed state is essential to obtain good monochromaticity. The spatial distribution of the work function in the emitter surface is also measured by the retarding potential method. The variation of φ, which limits the ultimately attainable monochromaticity with the near‐threshold drive method, is measured as 0.05 eV. It is estimated that ΔEless than 0.2 eV could be attained by the near‐threshold drive if the insulator thickness andVdare further reduced.

ISSN:1071-1023    

DOI:10.1116/1.588104

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

An analysis of the thermomechanics of metal (chiefly molybdenum) field emitters under normal operating conditions is given. The focus is on various ‘‘intrinsic’’ phenomena and the possibilities of triggering catastrophic breakdown. The heating is found to be predominantly Nottingham in origin (as opposed to ohmic) and is not appreciable unless the currents are well beyond the normal operating regime, e.g., as might occur under arcing conditions. As a result, the increases in temperature in operating tips are generally minimal unless the heat sinking to the substrate is weak, e.g., in ultrasharp tips, in tips on long, narrow posts, and/or in tips with severely degraded thermal conductivity. Apart from these exceptions, the small temperature excursions mean that no thermal runaway, melting, thermal desorption, or other direct thermal effects occur. Thermal stresses are of course also minimal; however, Maxwell stresses can be large under normal operating conditions, approaching the yield strength under high bias conditions.

ISSN:1071-1023    

DOI:10.1116/1.588105

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Schemes using chemical mechanical polishing of copper have been proposed for the patterning of interconnections in copper multilevel metallization. In this article, the phenomena involved in the removal of copper during copper chemical mechanical polishing are investigated. The concentration of chemical etchant in the polish slurry is varied to investigate the chemical component, and the applied pressure is varied to investigate the mechanical component. Two slurries, an ammonium hydroxide plus ferricyanide slurry and a nitric acid slurry, are used to polish both copper and Cu2O thin films. Removal of copper or Cu2O is hypothesized to be a result of mechanical abrasion, while the role of the chemical etchant is to dissolve the material abraded from the surface rather than to etch the material directly from the surface.

ISSN:1071-1023    

DOI:10.1116/1.588106

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

SiO2/Si systems with the SiO2films produced by plasma‐enhanced chemical vapor deposition (PECVD) usually have a high density of interface traps (Dit) as compared to those with the SiO2films grown thermally because in the former the systems have been subjected to plasma radiation. To simulate the radiation effects due to microwave plasmas during the deposition of SiO2films by PECVD, we used high‐quality thermally grown SiO2films to form SiO2/Si systems and studied the changes of the behavior of such systems after being exposed to microwave plasmas at various device temperatures. The results show that for SiO2/Si systems without metallic electrodes, the density of electron‐trapped charges,Qot, in the SiO2bulk andDitare higher after plasma radiation. For SiO2/Si systems with aluminum electrodes on the oxide and the Si surfaces, the effects of plasma radiation on the values ofQotandDitare less, indicating that aluminum electrodes act as protective layers partly screening the plasma radiation, but the penetration of vacuum ultraviolet light from the plasma to the SiO2bulk produces electrons and holes in SiO2bulk, which react with oxygen vacancies in the SiO–Si (nonbridging) bonds forming positive trapped charge in the SiO2bulk and at the SiO2/Si interface. The value ofDitincreases with increasing SiO2film thickness and decreases as the device temperature is increased from 25 to 200 °C during radiation. A further increase in device temperature beyond 200 °C leads to a reverse trend, implying that the defect generation and annihilation processes take place simultaneously during plasma radiation. Annealing in a forming gas at 400 °C removes most of the radiation‐induced defects. It should be noted that under a PECVD situation the radiation damage could be much worse particularly at the beginning of the PECVD process whereas the SiO2film is still very thin.

ISSN:1071-1023    

DOI:10.1116/1.588107

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

This article describes a study of gate oxide loss at the gate periphery of a metal–oxide–semiconductor field‐effect transistor (MOSFET) resulting from a polysilicon gate etch with a commercially available low pressure, high density plasma helicon etch tool. When the oxide is removed at the periphery of a MOSFET with the gate etch process, it is possible to damage the underlying silicon in the source and drain regions leading to device degradation or failure. Conventional oxide thickness and scanning electron microscope measurements after the gate etch have been shown to be inadequate in detecting microtrenches and microholes in the oxide at the gate periphery. To measure the integrity of the oxide at the gate periphery, a modified MOS (MMOS) capacitor test structure has been developed to measure the electrical field breakdown strength of the oxide at the gate periphery. This article describes a MMOS study of the oxide loss and underlying etch mechanisms encountered in a low pressure, high plasma density helicon etch tool.

ISSN:1071-1023    

DOI:10.1116/1.588053

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Scanning tunneling microscopy observations of the growth of Cl‐induced etch pits on Si(100)‐2×1 lend themselves to quantitative determinations of vacancy size distributions, particularly those that are linear or branched at some point along the linear pit. These result in rate constants and energy differences for the dominant etching channels. By considering nearest‐neighbor and second‐nearest‐neighbor interactions, we determine the attractive interaction energies between dimers in a row, 0.28 eV, and between dimers in adjacent rows, 0.22 eV, as well as the repulsive second‐neighbor dimers, −0.08 eV. These results are tested by means of Monte Carlo simulations.

ISSN:1071-1023    

DOI:10.1116/1.588054

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Selective reactive ion etching of Si over Si1−xGexand Si1−xGexover Si has been demonstrated by using a modulation‐frequency, plasma‐etch technique which employs CHF3and H2as the etch precursor gases. The selective etch crossover region appears at a modulation frequency of 2–3 Hz for a duty cycle of 50%. It is suggested that the etch selectivity phenomenon arises from the relative ion‐assisted and purely chemical components of the radio frequency plasma and decaying plasma afterglow.

ISSN:1071-1023    

DOI:10.1116/1.588055

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The effects of several chemical treatments on ZnSe surface composition and morphology have been analyzed with scanning electron microscopy and Auger electron spectroscopy. Polycrystalline bulk and thin film ZnSe heteroepitaxed onto GaAs were used. Large variations in the etching rate and surface conditions, such as roughness, contamination, oxides, and stoichiometry, have been observed with different etchants. Contamination by carbon and oxygen was present on all the treated surfaces. Surface oxides could be thinned by dipping in HF or HF/NH4Cl, which did not etch ZnSe. Methanol with 1% bromine etched ZnSe vigorously and selectively, and resulted in a rough surface. A relatively smooth ZnSe surface resulted from etching in NH4OH/H2O2, but excess Se precipitated from this solution to form whiskers. These whiskers could be removed using CS2. No excess Se was found after etching in hot NaOH but a thicker oxide and a pitted, rough surface was observed.  A two stage etch consisting of NH4OH/H2O2followed by CS2is recommended for a smooth, near‐stoichiometric surface.

ISSN:1071-1023    

DOI:10.1116/1.588056

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The influence ofinsituargon cleaning of GaAs on the electrical characteristics of Schottky diodes and metal–semiconductor field‐effect transistors (MESFETs) is investigated. The beam energy was varied from 50 to 500 eV and the characteristics were compared to wet chemically cleaned devices. The characteristics of the Schottky diodes showed a significant degradation as a consequence of damage introduced by argon cleaning. Recovery was obtained with an additional annealing step at 300 °C for diodes cleaned at energies below 125 eV. For higher energies, the samples became worse with annealing. MESFETs showed degraded performances for positive gate voltages due to a high gate leakage current. Improvement was also obtained upon annealing.

ISSN:1071-1023    

DOI:10.1116/1.588057

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

In order to understand the mechanism of the Cl2‐etching reaction with GaAs, the composition and reconstruction ofinsituCl2‐etched GaAs surfaces were studied as functions of the etching temperature. From an Auger electron spectroscopy analysis and reflection high‐energy electron‐diffraction observations, it was shown that the GaAs surface changed from As stabilized to Ga stabilized during low‐temperature (∼50 °C) etching, while it remained As stabilized during high‐temperature (150–250 °C) etching. This result can be understood by considering the temperature dependence of the desorption rate of chloride compounds. At low temperature, the desorption of Ga chlorides is more suppressed than that of As chlorides, resulting in rough Ga‐stabilized surfaces. At high temperature, the desorption of any chlorides is not suppressed. Thus, stoichiometric etching is realized, resulting in smooth As‐stabilized surfaces, which are advantageous for high‐performance microdevice fabrication.

ISSN:1071-1023    

DOI:10.1116/1.588058

出版商:American Vacuum Society    

年代:1995

数据来源: AIP