摘要:

In this paper we describe a method for performing proximity correction of very large scale integrated circuit layout data that is applicable for use on the AEBLE‐150 electron‐beam lithography system in particular, and other dose modulated systems in general. The algorithm employed saves computation time and program space by retaining, insofar as possible, the pattern hierarchy. The problem of instances of a cell which are in different environments is addressed by high‐speed environment estimation through construction of equivalence classes. The dose computation algorithm requires edges to develop at designed locations, rather than requiring constant average exposure as in the so‐called ‘‘self‐consistent’’ approach. Certain heuristics are employed to accelerate the computation. Dose contributions of rectangular areas are computed via look‐up tables and simple arithmetic. A table look‐up approach is also applied for trapezoidal areas. The proximity correction computation is based on a multiple Gaussian equivalent scattering function. We will describe measurement techniques we have employed for extracting model parameters for use in the correction program. The performance of the program will be evaluated based on estimates of the various computational components.

ISSN:1071-1023    

DOI:10.1116/1.583971

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The efficacy of the GHOST proximity correction technique for achieving submicron linewidth control in electron beam lithography has been experimentally evaluated. Using the AT&T electron beam exposure systems, the GHOST parameters (correction dose, defocused beam diameter, and overlay accuracy) required for proximity exposure correction at 20 kV were determined via scanning electron microscopy and electrical linewidth measurement techniques. Optimum proximity correction conditions were established from a matrix of correction doses and correction beam diameters on two different substrates: chromium on glass and aluminum on silicon. On chromium, linewidth control of better than ±0.05 μm was obtained using a 3‐μm beam and a correction dose between 30% and 40% of incident, or with a 4‐μm beam and a 40% correction dose. Even better proximity correction was achieved on aluminum with a 5‐μm defocused beam and a 30% correction dose. In conjunction with the experimental data, a computer model was developed to interpret these results. The model assumes an elliptical profile for the incident GHOST beam rather than a Gaussian. Using this model, the tolerances on correction dose and defocused beam diameter for 0.5‐μm lithography on aluminum were determined to be 9% and 1.6 μm, respectively. The third GHOST parameter investigated, overlay accuracy between the incident and GHOST exposures, was also found to be critical. A 0.5‐μm overlay error resulted in a 0.05‐μm linewidth deviation across a 0.5‐μm line and space pattern. Last, it was found that with AZ‐2400‐17 resist the loss of resist thickness and developer latitude upon GHOSTing will not result in pinholes or degrade process latitude as long as the correction dose is maintained at ≤ 40% of the incident dose, and a dilute developer is employed.

ISSN:1071-1023    

DOI:10.1116/1.583972

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

An experimental cluster beam facility of the type used by Takagi was developed and tested. Since the cluster generation rate (of silver clusters in graphite crucibles) was small and not consistently observable, a basic study of the generation process was undertaken. Theoretical evaluation has revealed that clusters are formed on crucible internal surfaces and not in the vapor stream which passes out of the crucible through a nozzle, as had been assumed earlier. Experiments have confirmed this heterogeneous cluster growth model, showing that clusters occur consistently only when a temperature distribution is maintained within the crucible which favors cluster formation on surfaces near the crucible nozzle. A remaining problem is the low rate of cluster generation. This rate needs to be raised if metal clusters are to be used in practical film deposition apparatus. An alternative process which involves gaseous rather than metallic clusters is also under study. It is well known that isentropic expansion of gases, pressurized to a few atmospheres, results in homogeneous nucleation and can produce appreciable quantities of clusters with thousands of atoms. In order to utilize such gaseous clusters for film deposition applications, an assist mode is used in which films are grown by simultaneous vapor deposition and bombardment with energetic noble gas clusters. So far, a suitable cluster beam source has been developed, and deposition of gold films on GaAs substrates has been initiated, whereby ionized argon cluster beams provide the energy.

ISSN:1071-1023    

DOI:10.1116/1.583973

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.583975

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Photoablation of polymers by laser beams is a practical process for via holes preparation in polymeric insulators. Excimer laser photochemistry of polymers is actively considered for microlithography. The ablation rate is dependent on the absorption coefficient. By addition of a dopant, photoetching rates of polymers can be increased significantly. In the present study the photoetching rates of poly(dimethyl glutarimide) and chlorinated poly(methylstyrene) are studied with pyrene as a dopant with 308 nm of XeCl excimer laser.

ISSN:1071-1023    

DOI:10.1116/1.583976

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Bombardment of silicon surfaces by low‐energy oxygen ions has been investigated as a possible process for growing films of SiO2at room temperature. Broad ion beams of energy 40–200 eV and variable oxygen content have been used to grow ultrathin oxides of extremely uniform thickness. The ion beam oxides are similar to thin thermal oxides in many respects—composition, chemical binding, optical, and electrical properties. The dependence of the thickness and quality of the oxide films on ion dose, ion energy, and substrate temperature have been investigated. The obtained thickness is observed to vary only slightly with increasing substrate temperature up to 650 °C which indicates nonthermal process kinetics. The ion‐beam oxides reach a limiting thickness of 40–60 Å which is largely independent of ion dose and is also found to be insensitive to ion energy. The observed oxidation is explained on the basis of surface implantation and radiation‐enhanced diffusion and reaction processes. Limited thicknesses are observed even when sputtering is negligible because of the decreasing effective penetration of the ions due to the swelling of the target which accompanies the conversion of Si to SiO2. Thus the film grows until the oxide–semiconductor interface moves beyond the current‐ion penetration depth after which oxidation effectively stops. This model is equally applicable to high‐energy, high‐dose oxygen‐ion implantation for production of buried oxides in silicon‐on‐insulator technology where it is observed that oxide growth occurs predominantly at the upper interface.

ISSN:1071-1023    

DOI:10.1116/1.583977

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Silicon dioxide thin films have been grown by the technique of photochemical‐vapor deposition. Deposition was performed using direct dissociation of oxygen by an ultraviolet arc lamp in the presence of silane. The films were deposited for a temperature range of 150 and 350 °C. Deposition rates peaked at a total pressure of 2 Torr, with a rate of 23 nm/min and 68 nm/min at 150 °C and 250 °C, respectively. Film stress is compressive with 1.04±0.14×109dynes/cm2. Dielectric constant (εox) and breakdown voltage (VB) were measured as 3.6 and 3.2 MV/cm, respectively. Etch rate in a room temperature 1:5 buffered hydrofluoric acid:deionized water solution was below 50 Å/s. The films have promise for application in integrated circuit devices.

ISSN:1071-1023    

DOI:10.1116/1.583978

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Uniform SiO2films of 0.1∼1  μm thickness were deposited on Si substrates (5 in. in diameter) by dual ion beams (DIB) which consists of ionized cluster beams (ICB) and ionized gas beams (IGB). In the source of ICB, fine powder of SiO is vaporized to form a jet stream, which on being ejected from a multinozzle into a high vacuum chamber, is cooled and clustered by adiabatic expansion. The clusters thus obtained are partially ionized in an electron shower, accelerated, and made to bombard the Si substrate. On the other hand, in the source of IGB, O2gas molecules ejected from a nozzle are partially ionized, excited in an electron shower, accelerated, and made to bombard the Si substrate too. These two beams collide and combine together on their way to the substrate or on its surface. The properties of the SiO2films formed by the DIB mainly varied with oxygen partial pressure, oxygen ion current density, and deposition rate; with an oxygen partial pressure of 6.7×10−2Pa, an oxygen ion current density of 6×10−7A/mm2, and a deposition rate of below 1200 Å/min at a substrate temperature of below 200 °C, the SiO2films obtained had an infrared spectrum peaking at 1060 cm−1with a half‐width at the half‐maximum of 80 cm−1. It indicates that the DIB can produce at a very low temperature with a very high deposition rate almost the same quality SiO2films as those obtained by thermal oxidation. This is considered to be possible because of the existence of the ionized and exited gas molecules and the migration of ionized clusters onto the surface of the substrate.

ISSN:1071-1023    

DOI:10.1116/1.583979

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

An ion streak camera has been constructed for measurement of time and angle correlations in ion emission from liquid‐metal ion sources. Emission events are detected with a chevron microchannel plate multiplier (MCP) as a fan of the ion beam is electrostatically deflected across the plate. The intensified images on the phosphor of the MCP are recorded in a digital video camera synchronized with the sweep. The images are then digitized and Fourier transformed to obtain two‐dimensional power spectra in frequency and angular wave number. Experiments have been performed using sweep times of 100 ns to 10 μs. The time behavior of the emission has been examined for low‐current direct current beams and for beams for which the extractor of the source has been driven at 2 MHz. Preliminary results for the power spectra are presented and discussed for these different cases.

ISSN:1071-1023    

DOI:10.1116/1.584046

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

An ion beam decelerator for energies down to 5 eV is described. The decelerator is a Menzinger retardation system that has been modified according to the results of calculations using a ray tracing model to optimize lens geometry. Performance tests of the decelerator demonstrate that H+2beams with currents ≥20 nA can be obtained with a spot size adjustable from 0.5 to 10 mm using a beam raster system.

ISSN:1071-1023    

DOI:10.1116/1.584047

出版商:American Vacuum Society    

年代:1988

数据来源: AIP