摘要:

Fast electron pattern generator (FEPG) is a variable shaped beam lithographic system specially designed for direct writing on wafers and for mask fabrication. Experimental results are given: gold gratings on silicon patterned with 10×0.3 μm spots, 1 μm gate field‐effect transistor (FET), masks 1×. All these results performed with a 5 A/cm2current density are consistent with a 1 μm technology. When the spot current exceeds 5 A/cm2, defects due to the space charge effect appear. Thermal effects on glass substrates are pointed out.

ISSN:1071-1023    

DOI:10.1116/1.583397

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Fast electron pattern generator–high resolution (FEPG‐HR) is a variable shaped electron beam system, derived from FEPG, specially designed for submicron direct writing, while keeping the multipurpose capabilities. Quarter‐micron linewidth is expected, thanks to a high demagnification of the stencil, reduction of the space charge effect, improvements in accurate metrology, and automatic calibration.

ISSN:1071-1023    

DOI:10.1116/1.583398

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The crossover of a thermionic electron gun acts as the virtual source in conventional electron beam lithography systems employing critical illumination as well as those employing Koehler illumination [Broers,SEM(IIT Research Institute, Chicago, 1979)]. The concept of critical Koehler illumination [Essig, IBM Tech. Discl. Bull.27, 1224 (1985)] combines critical illumination and Koehler illumination to image the cathode surface as the real source of the electrons into the probe shaping aperture and finally onto the target plane (window ray trace). Further on, the crossover as the virtual exit pupil of the gun lens is imaged into the entrance pupil of the final lens (pupil ray trace). Thus, in critical Koehler illumination, the linked beam concept consequently correlates conjugate planes of a probe forming system to those of the electron gun. The implementation of critical Koehler illumination in shaped beam lithography systems requires a special imaging mode of the electron gun. A typical triode gun can provide imaging of the emitter surface. Critical Koehler illumination has a high current efficiency, and the cathode supplies only the number of electrons needed in the target plane, so that maximum cathode lifetime and minimum electron–electron interaction in the beam result. Beam stability and spot image quality are substantially improved.

ISSN:1071-1023    

DOI:10.1116/1.583399

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

In a recent paper [McCord and Pease, J. Vac. Sci. Technol. B3, 198 (1985)] we described how it should be possible to generate, for lithography and other materials processing, an electron beam with an extraordinary combination of high current (>1 mA), low voltage (<100 V) and small diameter (<0.1 μm) using a modified scanning tunneling microscope (STM) operating in the field emission mode. To test this prediction we have built a modified STM onto the stage of a scanning electron microscope (SEM) so that we can monitor system geometry. The tip, an etched tungsten wire, can be manually moved in thezdirection (normal to the target) for coarse motion and three PZT piezoelectric transducers allow 10 μm travel in thex,y, andzdirections. A feedback system stabilizes the field emission current (and hence the tip‐to‐target spacing). We have obtained beams with currents from 1 nA to several microamps at voltages from 1 to 1000 V. We have used the beam to produce lines of contamination on a gold film; the contamination was then used as a mask against sputter etching to produce gold lines. In addition we have exposed a Langmuir–Blodgett resist film. In both cases we have produced sub‐tenth‐micron lines.

ISSN:1071-1023    

DOI:10.1116/1.583400

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

A new approach to electron projection is described which is suited to the design of an electron stepper. Electrons are emitted from the clear areas of a Cr mask by the interaction of short wavelength UV radiation with a CsI photocathode. A grid separates mask from wafer, creating a field‐free region into which conventional electron backscatter detectors may be placed to provide alignment signals. The system employs uniform electric and magnetic fields and the image size is limited only by the physical size of the grid. We calculate the distortion at the grid apertures and show that high resolution may be achieved by positioning the grid at the first magnetic focus and the wafer at the second. Experiments have been carried out in which submicron resolution is demonstrated and alignment signals are generated.

ISSN:1071-1023    

DOI:10.1116/1.583401

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

This paper describes several methods for the repair of stencil masks as used for electron‐ or ion‐beam shadow projection systems. Such a mask consists of a thin membrane about 3 μm thick with pattern as physical holes. The fabrication process is described elsewhere [H. Bohlenetal., inProceedingsoftheElectronandIonBeamScienceandTechnologyConference1978; U. Behringeretal. (unpublished)]. This mask may contain pinholes besides the desired pattern holes; also pattern holes may deviate from their designed size. The first step in the repair process is for a resist layer to be spun onto the whole mask area. Even larger holes with dimensions up to 1 mm are closed in such a way. In a second step, the resist layer is again opened at the pattern positions. We have investigated different methods to reopen the design pattern. The ‘‘block‐out’’ method uses a second transmission mask with an identical pattern. Owing to the statistical distribution of the defect holes, only the designed pattern holes will be reopened. The so‐called ‘‘writing methods’’ use a scanning e‐beam system to reopen the circuit pattern. The structural resist works as a substrate for a gold deposition from the reverse side of the transmission mask. After the gold deposition, this resist layer is removed by an O2plasma leaving behind a self‐supporting Au layer closing the undesired openings. Another repair method, the so‐called ‘‘darning method,’’ closes defect holes in the mask by contamination writing.

ISSN:1071-1023    

DOI:10.1116/1.583402

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

An electron image projection system has been developed which provides subfield or die‐to‐die alignment without mechanical motion of the mask or the wafer. This is made possible by a novel thin foil detection system which allows conventional alignment marks (i.e., etched grooves) and backscattered electron signals to be used for die‐to‐die alignment. Due to the fact that the wafer forms part of the imaging system in a photocathode projection system, any wafer flatness variation aggravates image distortion. This has made it very difficult to achieve accurate level‐to‐level overlay using a global alignment technology. The new alignment technique described provides a means of detecting alignment marks surrounding each die or subfield. The alignment marks can be placed in the scribe streets of the wafer, thereby not occupying valuable active areas. The foil detector is placed between mask and wafer and is biased in order to not distort the imaging field. Experimental results of image distortion and alignment sensitivity measurements indicate feasibility of this technique.

ISSN:1071-1023    

DOI:10.1116/1.583355

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The phenomenon of avalanche breakdown in silicon devices is often accompanied by a current into insulating layers leading to serious degradation, on the one hand, or to practical use in nonvolatile memories on the other hand. By injection of hot electrons towards the gate of a metal‐oxide semiconductor (MOS) device, the oxide and/or floating gate is charged. The large initial current is rapidly reduced by this space charge. By removing the oxide at the site of injection, in a structure optimized for its purpose, the electron current can be injected into vacuum. Lowering the work function with, e.g., cesium enhances the vacuum current several orders of magnitude to levels where it can be of practical use. This use is demonstrated in a simple (small) TV tube which already operates hundreds of hours without appreciable degradation. Basic principles and design aspects as well as technological aspects are discussed.

ISSN:1071-1023    

DOI:10.1116/1.583356

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The emission properties of cesiated silicon cold cathodes are described and the factors which ultimately limit the performance of such cathodes are discussed. It is tentatively concluded that the maximum available current density and brightness are limited by cesium migration and desorption, these maximum values (for emitters with 1 μm diam and with an efficiency of 1.5%) beingjvac,max≂1500 A/cm2andBmax≂9×106A/cm2sr (atV=10 kV). The long term stability of the emission is surprisingly good, in spite of adsorption of oxidizing gases from the vacuum. This indicates that there is a desorption of such gases too, probably due to the outgoing electrons at high current densities.

ISSN:1071-1023    

DOI:10.1116/1.583357

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Single crystal LaB6has become an important cathode material for a variety of electron beam systems. At the typical operating pressures of many such systems interaction of the cathode with the residual gases present can cause radical enhancement of the cathode volatility with concomitant change in the usual conical shape, oxygen‐bearing gases being the most active in promoting such effects. In this paper we discuss a systematic investigation of the variation of volatility and morphology of heated LaB6cathodes with oxygen pressure. The results of this study show that at a low operating temperature of 1600 K the volatility enhancement due toPO2=1×10−6Torr is almost a factor of 100 relative to operation at 1×10−8Torr or less. In contrast, at a cathode operating temperature of 1900 K the enhancement due to the same oxygen pressure is negligible. The volatility enhancement of LaB6forPO2=1×10−7Torr andT=1700 K is only a factor of 2. The volatility enhancement was observed to vary with crystallographic direction and is primarily responsible for the well known formation of facets on an initially conical emitter structure. From the relative rates of growth of the various facets we were able to conclude that crystal face anisotropy of the oxygen enhanced volatility of LaB6increases in the order (110)<(111)<(100). In the case of a truncated conical cathode the results show the expected increase in rate of change to a pointed pyramid final shape as the cone angle is decreased from 90° to 70°.

ISSN:1071-1023    

DOI:10.1116/1.583359

出版商:American Vacuum Society    

年代:1986

数据来源: AIP