摘要:

In the present work inclined incidence of accelerated electrons to solids is simulated using Monte Carlo technique. Spatial distributions of absorbed electron energy density in a 125 nm poly(methylmethacrylate) resist layer on bulk Si substrate are obtained for angles of incidence 30°, 45°, and 60° at two beam energies—25 and 50 keV—together with the energy and angular distributions of the backscattered electrons. The results show strong asymmetry of the exposure distributions. Their peaks are significantly lower, wider, and 40–100 nm shifted, and their shapes are different in comparison with those for normal incidence of electrons. The ratio between the maximum values of exposure distributions due to the forward scattered and the backscattered electrons decreases with decreasing angle of incidence. These peculiarities of exposure distributions may lead to enhanced proximity effects and cause deviation from required pattern shapes. Therefore, if inclined incidence of accelerated electrons to any surface occurs during electron beam lithography, it has to be taken into account.

ISSN:0734-211X    

DOI:10.1116/1.588754

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Radial and azimuthal distortion aberrations are increasingly a function of the image side lens bore radius in the range from 1.25 to 5 times as large as the maximum image field radius. This phenomenon is inconsistent with our previous understanding. An assumption is made that these large distortions for the large bore radii come from the influence of the magnetic field of one on the other, thereby destroying the symmetry. This assumption is confirmed from the following simulation. When these distortions are calculated for the ideal case where the magnetic fields are calculated in the condition without the other lens, they are decreased to around 1/10 of those for the case where the magnetic fields are calculated in the real condition with the lenses in proximity. When the object–image distance is 800 mm and the bore radii of lens 1 are 100 and 20 mm, the residual radial and azimuthal distortions are 1.5 and 0.7 nm, the beam blur is smaller than 45 nm for the beam semiangle from 0.05 to 0.7 mrad, where the main‐field and subfield sizes in the image plane are 20 mm and 250 μm, respectively, the beam energy is 100 keV, and the space charge effects are neglected.

ISSN:0734-211X    

DOI:10.1116/1.588755

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Proximity effect correction for reticle making by the dose correction method is discussed. A new algorithm for calculating the optimum dose is proposed, which is based on the dose formula method and the representative figure method. Its main feature is that dose evaluation points are fixed at individual small regions whose size is sufficiently small compared with the backscattering range. The calculation speed of the computer is evaluated which is sufficient to suppress the correction time to less than the writing time. The required calculation speed is 500 MIPS×4 CPU at most for a minimum feature size greater than 0.2 μm on the reticle. This result suggests that the real‐time proximity effect correction is possible for making reticles. Furthermore, when the algorithm is applied to x‐ray mask fabrication and direct writing process, the calculation time can be suppressed to less than the writing time.

ISSN:0734-211X    

DOI:10.1116/1.588756

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Surface tension of substrates and layers used in semiconductor technology (e.g., Si, SiO2, Si3N4, AlCu, and WTi) as well as surface tension of materials of photolithography as resists and developers were determined by contact angle measurements. Resists and developers could be divided into two groups with polar and nonpolar behavior, respectively. The pretreatment of the substrates (cleaning, dehydration, and exposure to humidity) influences the surface tension. It was found that surface modification by primers, for example, hexamethyldisilazane and trimethylsilydiethylamine provides stable and reproducible surface tension. To reduce defect density of resist structures, a general optimization approach of surface tension was derived and successfully applied, using Si and AlCu as substrates in a typical photolithographic process. The results show a good adhesion of resist will be achieved if the work of adhesion is greater than 5 dyn/cm. A suggestion is given of process window of the contact angle is given for certain combinations of types of resist and developer.

ISSN:0734-211X    

DOI:10.1116/1.588757

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The characteristics of poly‐Si trench etching in high density plasma processes was studied by x‐ray photoelectron spectroscopy. Poly‐Si films on SiO2‐covered Si(100) substrates were masked with a 200‐nm‐thick oxide hard mask. The 200 mm wafers were then etched downstream using a helicon high density plasma source and a chlorine‐based gas chemistry. After etching, samples were transferred under ultrahigh vacuum to a surface analysis chamber equipped with an x‐ray photoelectron spectrometer. Regular arrays of trenches were used to determine the photoelectron signals originating from the tops, sidewalls, and bottoms of the features. A thin oxide film was found on the sides of the oxide masked poly‐Si trenches. The origin of this film can be related to the sputtering and redeposition of oxide from the quartz tube of the helicon source located in the plasma generation region. A substantial amount of chlorine was present on the poly‐Si sidewall of the features, whereas less chlorine was found on the oxide surfaces. The poly‐Si sidewalls were covered by a small amount of oxygen.

ISSN:0734-211X    

DOI:10.1116/1.588758

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

This article reports on a study of the photoluminescence (PL) characteristics of SiO2/Si/SiO2quantum well structures formed by the thermal oxidation of Si lines with rectangular cross sections and (111) side planes. The PL spectra have a peak at a wavelength of 760 nm regardless of Si width, indicating that the emission is due to the recombination of carriers at the Si/SiO2interface. The Si width required to obtain the maximum emission is about 5 nm, which is thicker than theoretically predicted. The reason for this is clarified by measuring the difference in the PL characteristics for patterned and unpatterned SiO2/Si/SiO2film structures. In the film structures, the characteristics are found to vary by the patterning of the ultrathin Si layer, followed by oxidation; the Si thickness yielding the maximum intensity increases and a wide range of Si thickness contributes to the emission. This behavior is consistent with that of the oxidized Si lines and is possibly due to pattern deformation caused by oxidation. The stress accompanying the deformation is probably the reason for the increase in the PL intensity in thicker Si. Therefore, the PL characteristics for Si are strongly influenced by the patterning and subsequent oxidation.

ISSN:0734-211X    

DOI:10.1116/1.588759

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A computer simulation has been carried out to study the dynamics of pore formation in porous silicon. Porous structures were generated by a simple three‐dimensional Monte Carlo calculation, based on a modified percolation model for pore growth in lightly and heavily doped silicon substrates. The results are consistent with recent observations. As an approximate guide, the type formed morphology was shown to depend mainly on the doping level of the substrate. A strong dependence of the average porosity on the doping level of the substrate is also predicted.

ISSN:0734-211X    

DOI:10.1116/1.588760

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Etching of polysilicon features using a helical resonator plasma source is evaluated. Performance metrics consist of etching rate, etching rate uniformity, and profile control using HBr/O2–He gas‐phase chemistry. The effect of source power, rf‐bias power, and reactor pressure on etching rate and uniformity is examined using a response surface experiment. Feature profile control is determined by examining nested and isolated lines and trenches using oxide mask/polysilicon/oxide structures. Good uniformity and vertical profiles are obtained at low reactor pressures, high source power, and rf‐bias between 50 and 60 W. The operating point for best uniformity is at 3.5 mTorr, 3000 W source power, and 53 W rf‐bias power. At this point, the etching rate is 3700 Å/min and the nonuniformity is less than 1.0%, over 125‐mm‐diam wafers. Radial profiles of electron temperature and ion density near the wafer surface are presented as a function of source power, rf‐bias power, and reactor pressure. The ion density was found to be in the mid‐1011cm−3range and electron temperatures were 5–7 eV. An increase in source power and reactor pressure results in an increase in ion density; however, the electron temperature shows a weaker dependence. Finally, these results are compared to those using helicon and multipole electron cyclotron resonance plasma sources evaluated in previous studies. We found that all three plasma sources provide high ion density at low pressures to meet performance demands for polysilicon etching; however, the helical resonator source offers somewhat higher etching rate and better bulk plasma uniformity.

ISSN:0734-211X    

DOI:10.1116/1.588761

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Temperature‐dependent surface morphologies of Si(100) resulting from Br etching at 700 and 800 K have been studied using scanning tunneling microscopy. Quantitative analysis of linear pit distributions allows us to interpret the mechanisms involved in surface pattern formation. We show that linear chains growing at 800 K on 450‐Å‐wide terraces are in quasi‐steady‐state conditions in that their lengths follow the most probable Flory–Schulz distribution. Results obtained under equivalent conditions at 700 K, however, demonstrate that this distribution is not reached. The difference reflects the rate of step retreat relative to the rate of pit growth. At 700 K, pits that develop on terraces are erased before their length distributions reach quasi‐steady‐state values even though the overall morphology does not change. The surface morphologies that are reached at long times can then be understood by considering the temporal evolution of linear chains on terraces where quasi‐steady‐state conditions are not fulfilled.

ISSN:0734-211X    

DOI:10.1116/1.588762

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

An ultrahigh vacuum compatible planar corrugated millimeter mm‐waveguide structure (410‐μm‐deep) possessing bi‐fold symmetry and a precision beam aperture (800 μm) has been fabricated using silicon processing technology, modeled with numerical analysis software, geometrically characterized, and compared to a similar waveguide fabricated using deep x‐ray lithography (DXL) techniques. The waveguide was fabricated to operate at 60 GHz (λ=5 mm) with fields suitable for 2π/3 phase advance operation. Multichip alignment technology was used to provide a semiclosed conducting surface with aperture‐coupled periodic resonator cavities. A pair of Si/Pyrex composite metallized substrates patterned with corrugated geometries have been vertically stacked with 980‐μm‐diam Pyrex capillaries. Geometrical analysis of the muffin‐tin waveguide was divided into two classifications: substrate feature error and die‐to‐die orientation error. Both types of error were characterized with the following results: feature accuracy was maintained to 0.1%–1.0% tolerances in all directions (5 μm or less in most cases) and die‐to‐die aperture distance agreed to within ∼3% of theoretical calculation. Methods of improving these geometrical tolerances are suggested and critical issues are addressed. Electromagnetic testing of the mm waveguide has been investigated and a bead was fabricated for use in a bead‐pull perturbation measurement of acceleration properties. The concluding section compares deep‐etch silicon and DXL approaches for the fabrication of the ‘‘micro‐linac.’’ It is concluded that through further refinement of thermal and conductive properties that the silicon waveguide is a viable method of constructing a micro‐linac mm waveguide, requiring less fabrication complexity, processing time, and capital equipment investment than DXL.

ISSN:0734-211X    

DOI:10.1116/1.588763

出版商:American Vacuum Society    

年代:1996

数据来源: AIP