摘要:

Vacuum microelectronics (VME) concerns the design and manufacture of vacuum devices and components built to sizes and tolerances similar to those found in solid state microelectronic devices. This technology is well suited for use in electron devices of commercial importance, particularly flat‐panel displays. The flat‐panel display industry is projected to have annual revenues measured in the tens of billions of dollars by the turn of the century. As opposed to conventional electron tubes that utilize cathodes based on thermionic emission, vacuum microelectronic devices principally utilize cold cathodes based on field‐electron emission. The introduction of field‐electron emission cathodes can yield unique device performance; however, attaining the level of reliability required for commercial applications requires addressing a host of challenging surface physics and chemistry problems. In this review we outline the surface‐science‐related issues of importance in VME. These issues cover a large realm of surface science ranging from adsorption/desorption phenomena, surface diffusion, surface passivation, and the deposition of overlayers to cathode bombardment, field‐electron current density limits, emission noise, low‐voltage phosphors, thin‐film growth, and voltage breakdown. As the field of VME is relatively new, many of these surface aspects have not been thoroughly investigated and many more remain to be identified.

ISSN:0734-211X    

DOI:10.1116/1.588219

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Scanning tunneling microscopy (STM) imaging of four nucleic acid bases, adenine, guanine, thymine, and cytosine, has been performed on the surface of SrTiO3single‐crystal substrates. The images indicate that the bases are deposited as individual molecules in ultrahigh vacuum condition, and can be individually observed by STM. A comparison of the heights and lateral dimensions of the deposited species and also the bias dependence of the heights, enables differentiation between four nucleic acid bases in real space.

ISSN:0734-211X    

DOI:10.1116/1.588220

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The scanning force microscope has been used to study the lattice and defect structures of multilayers of the unsaturated fatty acid, 12‐8 diacetylene (10,12‐pentacosadiynoic acid) in ambient conditions. Films were prepared by the Langmuir–Blodgett technique on ordinary microscope glass and indium tin oxide coated glass. Lattice structures were deduced from the well resolved molecular images and, before polymerization, were found to be nearly centered rectangular with lattice parameters (0.88±0.06) nm and (0.51±0.04) nm. After exposing to ultraviolet radiation for polymerization the lattice structure changed to an oblique lattice with lattice parameters (0.466±0.008) nm and (0.55±0.01) nm. Molecular level defects such as dislocations and grain boundaries were resolved in these films very clearly. Observation of these kinds of defects implies that it is possible to reliably image the real surface molecules under ambient conditions. Polymerization was found to take place in one of the lattice directions and the modulation perpendicular to that direction was more pronounced than along the polymer backbone.

ISSN:0734-211X    

DOI:10.1116/1.588164

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Local modification of H‐terminatedn‐Si(100) surface in an aqueous hydrofluoric acid (HF) solution was carried out under anodic and cathodic potential polarization with aninsituscanning tunneling microscope (STM). Two different modifications in the HF solution were obtained. At cathodic polarized potential, H‐terminated silicon surface is attacked by HF at the defects of silicon surface under an electric field between the tip and silicon surface. However, at anodic polarized potential (by applying positive potential pulses), the nanostructures produced are probably due to the formation of silicon oxide. The apparent depth of the nanostructures, as observed with the STM, decreases with time because of the dissolution of silicon oxide in the solution. Effects of the tunneling current, the potential of silicon surface, and pulse amplitude show that the formation of silicon oxide is dependent on the electric field and local electrochemical oxidation of silicon surface at anodic potential.

ISSN:0734-211X    

DOI:10.1116/1.588165

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A novel fabrication process for uniform ultrafine SiO2gaps with perfectly vertical sidewalls is proposed and experimentally demonstrated. The gaps without undulation were successfully fabricated by splitting the SiO2layer along the guidelines established beforehand, utilizing thermal stress between the SiO2layer and the InP substrate. High uniformity of the gap width of less than 5% along 200 μm has been obtained. Minimum gap width of 20 nm has been realized. Moreover, this ‘‘split mask’’ was found to be applicable as a selective regrowth mask and a dry etching mask.

ISSN:0734-211X    

DOI:10.1116/1.588166

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The surface topography of doped polysilicon films was investigated by atomic force microscopy for a wide range of doping and process conditions. These low‐pressure chemical vapor deposition silicon films were approximately 350 nm thick. The amorphous films wereinsituphosphorus doped during deposition at 550 °C, while the crystalline films were deposited at 625 °C and subsequently diffusion doped using either PH3or POCl3gases. Measured resistivities ranged from 700 to 10 000 μΩ cm corresponding to secondary ion mass spectrometry phosphorus concentrations that ranged from 8.45 to 0.95×1020cm−3.Insitudoped films exhibited the smoothest surface topography with a peak‐to‐valley surface roughness of 11 nm. The surface roughness values were 50 nm for PH3doped poly films, and as high as 135 nm for the POCl3doped films. Atomic force microscopy grain size analysis showed uniform distributions for theinsituand PH3doped films with grain sizes of 130 and 200 nm, respectively. POCl3doped poly‐Si showed bimodal grain size distributions, with the secondary grains measuring 500 nm in size and the normal grains averaging 225 nm. These secondary grains increased the surface roughness and their occurrence correlates with chlorine concentration. The number of secondary grains and their size increases with higher phosphorus content. Following the polyoxide growth, the surface roughness increased 3× to 5× with POCl3doping, but the surface topography increased only slightly for PH3andinsitudoped poly‐Si. After removing the polyoxide, the surface roughness decreased for the diffusion doped films.Insitudoped films retained their smooth surface following the oxidation and removal of the oxide.

ISSN:0734-211X    

DOI:10.1116/1.588167

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Epitaxial growth of Si on Si(100) wafers was carried out at 700 °C in an Ar microwave electron cyclotron resonance plasma chemical vapor deposition system. Both plasma exposure prior to growth and epitaxial growth were monitored by real‐time single‐wavelength ellipsometry, first to determine an optimum end point for Ar plasma cleaning which would favor quality epitaxial growth, and second to follow the growth of the epitaxial film. Spectroscopic ellipsometry combined with cross‐sectional transmission electron microscopy and atomic force microscopy were used to characterize the epitaxial films, the epitaxial film/substrate interface, and the surface morphology. Secondary‐ion mass spectroscopy was used to evaluate the contamination levels at the film/substrate interface. Epitaxial films were successfully grown on both, smooth and rough (20–30 nm roughness layer) Si substrates. For both cases the top surface of the epitaxial film was smooth, but the interfaces were different.

ISSN:0734-211X    

DOI:10.1116/1.588168

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A variation in the reactive ion etch (RIE) rate of silicon oxynitride ( SiOxNy) films deposited by plasma‐enhanced chemical vapor deposition was studied by CHF3RIE, CHF3+carbon mono‐oxide (CO) RIE and CF4RIE. The source gas flow rate ratio (R=N2O/SiH4) during the SiOxNyfilm deposition was varied to obtain a film of different atomic composition. Etch rates decreased in the order of CF4RIE, CHF3RIE, and CHF3+CO RIE, and the etch selectivity of SiO2over SiOxNyincreased in the same order also. The fluorocarbon ( CFx) film deposited during a RIE process was analyzed by x‐ray photoelectron spectroscopy measurements. Etch rates are found to be correlated to both thickness and atomic composition of the CFxfilm. Carbon‐rich fluorocarbon films are found to be more resistive against RIE.

ISSN:0734-211X    

DOI:10.1116/1.588169

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Silicon dioxide etching technology for deep‐submicron ultralarge scale integration has been developed using an electron cyclotron resonance (ECR) plasma etcher. The optimum conditions for silicon dioxide etching are obtained in terms of etch rate, geometrical controllability, and radiation damage by fully utilizing such advantages of the ECR plasma etcher as low‐pressure operation, high plasma density, and independent control of ion energy and plasma discharge. High selectivity is also found at low pressures with C4F8/CH3F. The technology has been successfully applied to the formation of 0.35 μm contact holes with an aspect ratio of 4 without a decrease in etch rate.

ISSN:0734-211X    

DOI:10.1116/1.588170

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Anisotropic etching of deep SiO2has been obtained using electron cyclotron resonance–reactive ion beam etching with C2F6gas. The influence of total gas pressure and gas flow rate on the profile control and the roughness due to the etching have been determined. The sidewall angle of etched profile can be tailored by adjusting the processing conditions, and it is found that a sidewall angle of 90° for an etching of deepness around 18 μm is obtained at a pressure of 1.0 mTorr and a gas flow rate of 35 sccm. Low roughness has also been achieved for a pressure of 1.0 mTorr with the gas flow rate ranging from 25 to 40 sccm. Here, the scanning electron microscope and the scanning tunneling microscope have been used to study the etched profile and the roughness, respectively.

ISSN:0734-211X    

DOI:10.1116/1.588171

出版商:American Vacuum Society    

年代:1995

数据来源: AIP