摘要:

The semiconductor industry is moving toward the use of damascene processes for wiring of circuits on chips. These processes are based on the etching of vias and trenches into dielectric layers, filling these features with metal, and finally chemical–mechanical polishing, which results in a planarized, embedded feature. A two‐layer feature, typically a pad or trench with a via at the bottom which connects to some underlying contact is known as ‘‘dual damascene.’’ Ionized magnetron sputter deposition has been used to successfully fill these two‐layer features, both with AlCu and Cu metallurgies. This process uses conventional, commercial manufacturing‐scale magnetrons in combination with a dense, inductively coupled rf discharge to ionize a large fraction of the sputtered atoms. A small electrical bias on the sample then causes the metal ions to deposit at normal incidence, which results in dense fills at moderate aspect ratios (AR = 2:1) on room temperature samples.

ISSN:1071-1023    

DOI:10.1116/1.588004

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We have developed a technique recently for copper chemical vapor deposition utilizing direct liquid coinjection of trimethylvinylsilane (TMVS) and the copper (I) precursor (hexafluoroacetylacetonate) Cu (TMVS). We present here an investigation of the properties of copper films deposited using this technique. The films were grown on Si3N4substrates at temperatures in the range of 220–250 °C and characterized using several experimental techniques, with an emphasis placed on factors influencing copper film resistivity. The average as‐deposited film resistivity is 1.86 μΩ cm; this value is reduced to 1.82 μΩ cm when the effects of surface scattering are taken into account. The resistivity is essentially independent of film thickness for thicknesses between 0.2 and 3.5 μm, and is reduced by less than 0.05 μΩ cm by annealing at 400–600 °C in vacuum. The total impurity content of the films is approximately 100 parts per million. The film density is 97±2% of the bulk copper value. The average grain size increases with film thickness and falls in the range of 0.5–1.5 μm. Morphological defects are the main cause of the resistivities (after adjusting for surface scattering) being approximately 0.14 μΩ cm above the bulk copper value (1.68 μΩ cm). Comparison of thickness and resistivity measurements for rough as‐deposited films and smooth chemical‐mechanical polished films shows that the surface roughness causes surface profilometry to overestimate the thicknesses of the unpolished films by approximately 1300 Å. This effect can lead to both artificially high resistivity values and a false dependence of resistivity on film thickness if profilometry measurements for the unpolished films are not properly corrected.

ISSN:1071-1023    

DOI:10.1116/1.588005

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

This article discusses the impact of the line and space duty ratio and optical coherence on image quality fori‐line projection systems used in conjunction with alternated type phase shifters on projection masks. With a negative process, it was found that the alternated phase‐shifting method improve the depth of focus (DOF) for space patterns with a width smaller than the linewidth. On the contrary, there was no effect for narrow line patterns when the space width was larger than twice the linewidth. It was also found that the DOF became larger when the coherence became higher using both the alternated and the conventional mask for line patterns with a width smaller than the space width. It is concluded that high degree of optical coherence must be chosen for the phase‐shifting method. The alternated phase‐shifting method was applied to a bit line layer of 64 Mbit DRAM, and a DOF of 1.2 μm was obtained for both memory cells and peripheral patterns in which the minimum feature size is 0.35 μm. It is suggested that a negativei‐line resist with a large focus latitude at a high degree of optical coherence will be indispensable in applying phase‐shifting lithography to device fabrication.

ISSN:1071-1023    

DOI:10.1116/1.587971

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Optimization of electrostatic lenses was successfully achieved by using the cubic spline method or theapriorigiven multielectrode approach. In this article we propose optimization of electrostatic deflectors by using the cubic spline method for the purpose of attaining the minimum beam spot size. We propose the reconstruction of the electrodes of electrostatic spline deflectors in terms of the optimized first harmonic field distribution functions. Our calculations show that geometrical deflection aberrations can be reduced by 2–3 orders of magnitude.

ISSN:1071-1023    

DOI:10.1116/1.587972

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

In this article, simulation, fabrication, and direct current (dc) characterization data are presented for column‐based silicon field emitter array (FEA) devices, made using anisotropic or isotropic etching of silicon to form emitter tips. In the design of the fabrication process, we have attempted to minimize spatial nonuniformity of process parameters affecting the geometry of the device structure, and, where possible, counteract the nonuniformity through a proper choice of processing variables. FEA devices, with as many as 232 630 tips, on 4–10 μm centers, have been successfully fabricated. The highest electron emission current measured was over 18 mA at the gate voltage of 150 V for a 6648 tip array.

ISSN:1071-1023    

DOI:10.1116/1.587973

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Scanning force microscopy can routinely image supercoiled DNA molecules under liquids or in air and the complete three‐dimensional path of the chain can be identified. This makes it possible to evaluate the writhing number (Wr) of the coiled curve described by the chain axis in the imaged conformation of the molecule.Wris a much better descriptor of supercoiling than the linking deficit (ΔLk) which has been commonly used so far.Wrof the DNA axis curve can be roughly estimated by the signed‐intersection approach or calculated as the Gauss integral of the curve itself. We applied both methods to a model closed simple curve and to coiled DNA molecules exhibiting one or two turns of the chain about their superhelical axis.

ISSN:1071-1023    

DOI:10.1116/1.587974

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A new method for fabrication of reactive ion etching masks for nanoscale GaAs columns is proposed. The mask consists of sub‐100 nm Au islands formed byinsituheating a thin gold film on the substrate surface. The resulting areal density of the Au islands can exceed 1010cm−2. The islands show good resistance against etching, making the method suitable for fabrication of nanoscale structures with very high aspect ratios. This is demonstrated by etching over 1 μm high GaAs and AlGaAs/GaAs columns with widths below 100 nm.

ISSN:1071-1023    

DOI:10.1116/1.587976

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Optimization of thermally stable ohmic contacts to single doped, InP high electron mobility transistor (HEMT) structures was performed using AuGe–Au. Pulse doped and uniformly doped lattice matched HEMT structures were utilized to investigate the effects of doping profiles on contact resistance,Rc. The lowest contact resistance was obtained on pulse doped structures (Rc<0.1 Ω mm). Uniformly doped structures yieldedRc<0.2 Ω mm. AuGe–Au contacts were similarly fabricated on pseudomorphic HEMT structures incorporating an Al0.65In0.35As Schottky layer to monitor the change inRcresulting from the increase in band gap discontinuity. The use of a pseudomorphic Schottky layer resulted inRcof ≳0.3 Ω mm.

ISSN:1071-1023    

DOI:10.1116/1.587977

出版商:American Vacuum Society    

年代:1995

数据来源: AIP