摘要:

Self‐assembled monolayers made from long chain hydrocarbon trichlorosilanes have been used previously as very thin self‐developing resists, ideal for electron‐beam lithography. We are currently studying the physical and chemical effects of additional functional groups at the monolayer terminus by varying the electron‐beam dose and etching procedures for the fluorinated trichlorosilanes. These monolayers are attractive candidates for ultrathin electron‐beam resists because they are typically inert towards concentrated alkalis and acids thereby making them resistant to chemical attack. These materials can be used as positive resists on oxide surfaces at various electron‐beam energies and doses. A wet chemical etch is used to transfer exposed patterns to substrates.

ISSN:0734-211X    

DOI:10.1116/1.588436

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Electron‐beam lithography’s resolution limit is greater than the beam diameter due to resist limitations as well as electron interaction with solids. We examine the effect of molecular weight on the resolution of poly(methyl methacrylate) (PMMA). The experimental procedure uses thin Si3N4in order to reduce the backscattered electron contribution to the exposure, and the resist contrast standard deviation σ was determined. Molecular weights of 950×103, 120×103, and 15×103amu were used. It is found that relatively equivalent exposure and resolution are found in each case, and that the entanglement threshold is either lower than thought, or is not a factor in the resolution of PMMA. Lines as small as 7 nm are found in the highest molecular weight.

ISSN:0734-211X    

DOI:10.1116/1.588437

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Spherical and chromatic aberrations of electrostatic lenses with negative space charge in axial area are studied. A ‘‘toroidal subbeam’’ algorithm has been developed to model the evolution of the current and charge density distributions of intense charged particle beams taking into account space charge and initial thermal velocity effects. Optimized designs are presented which prove that negative spherical and chromatic aberration coefficients can be achieved for a space charge lens using an electron gun to produce the space charge cloud.

ISSN:0734-211X    

DOI:10.1116/1.588438

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

After etching in a helical resonator HBr plasma, polysilicon (poly‐Si) micron‐size features masked with photoresist (PR) were investigated with angle‐resolved x‐ray photoelectron spectroscopy and scanning electron microscopy to spatially resolve surface chemical compositions. The poly‐Si sidewalls and trench bottoms, and the PR sidewalls are covered with one to two monolayers of SiBr and SiBr2. No SiBrxspecies are present on top of the PR surfaces. No carbon or oxygen were detected on the poly‐Si sidewalls, suggesting that line‐of‐sight deposition of carbon from sputter erosion of the corners and sides of the PR does not occur. Because Br atoms react very slowly with poly‐Si, relative to the ion‐assisted etch rates, anisotropic etching does not require sidewall passivation from products of PR erosion. A SiBrxlayer does form on the PR sidewall, however, and could play a role in suppressing lateral erosion of the mask and improving profile control with HBr versus Cl2plasma etching.

ISSN:0734-211X    

DOI:10.1116/1.588439

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The topography of Si(100) surfaces is investigated by scanning electron microscopy after generating replicas using photoinduced dry etching with radiation predominantly in the wavelength range between 105 and 122 nm. XeF2and Ar mixtures provide high selectivity with a structural resolution of about 100 nm. Pores and grains indicate that single photons initiate chain reactions with an amplification of 3×105. The overall quantum efficiency of removed Si atoms per incident photon above unity leads to a probability for stimulation of a reaction per incident photon of 6×10−5. Addition of O2increases the amplification factor, reduces the excitation probability, and causes a reduced selectivity at high irradiation intensity.

ISSN:0734-211X    

DOI:10.1116/1.588440

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

High density plasma etching processes using chlorine gas have been developed for 0.25 μm polysilicon etching. Polysilicon films on SiO2‐covered 200 mm silicon wafers are masked with photoresist patterns, and then etched downstream using a high density helicon source made by Lucas Labs of Sunnyvale, CA. To enhance the anisotropic etching, ion bombardment is provided by radio frequency (rf) biasing of the sample. Polysilicon trenching can be suppressed by performing a two‐step etching process: the first uses a high energy ion bombardment resulting in high etch rate (250 nm/min) and anisotropy and the second a lower ion energy. The second etching step shows a high selectivity (≳80) of Si over SiO2and therefore ensures the complete removal of the polysilicon during the overetch time. Perfect anisotropic profiles can be obtained without any trenching or other undesirable anomalies. The optimum etch rate nonuniformity is 6.5% (3σ) when operating the source at maximum rf source power (2500 W), 2 mTorr reactor pressure, and adding 30 sccm of helium to a 50 sccm chlorine discharge. Polysilicon and gate oxide etch rates have been measured using a real timeinsituHeNe ellipsometer. Etch rates for polysilicon and oxide increase as a function of rf bias power but show no significant pressure or rf source power dependence. After etching, the 200 mm wafers can be transferred (under high vacuum) to an ultra high vacuum analysis chamber equipped with a Fisons ESCALAB 220i x‐ray photoelectron spectrometer.

ISSN:0734-211X    

DOI:10.1116/1.588441

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Deposition and patterning of Si/SiGe multiple stacks have been investigated byinsitumonitoring techniques. Reflection supported interferometry has been applied to evaluate the thickness and optical parameters of each of the films during the deposition of the stacks by rapid thermal chemical vapor deposition. During patterning by reactive ion etching of these stacks, the nonselectivity of the etch process has been eluded by monitoring of the 265.1 nm Ge line using optical emission spectroscopy. In this way an etch stop can be achieved within any of the thin films of the stack. The results demonstrate an opportunity forinsitucontrol, including end point detection of deposition and patterning of Si/SiGe multiple stacks.

ISSN:0734-211X    

DOI:10.1116/1.589034

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

We study the modifications on the three‐dimensional transport properties of Si‐doped AlGaAs layers exposed to CH4/H2reactive ion etching (RIE) by using the temperature dependence of Hall measurements. The persistent photoconductivity (PPC) effect is observed for the samples illuminated at low temperature (4.2 K). A strong capture region is observed between 100 and 160 K. Different annealing temperatures (between 300 and 450 °C) are used to study the effect of the passivation of Si donors and DX centers on the PPC. For annealing temperatures lower than 350 °C a new capture region is identified and attributed to the DX3 center. Also, the resistivity and mobility are modified by RIE exposure. The transport characteristics are recovered after thermal annealing at temperatures higher than 400 °C.

ISSN:0734-211X    

DOI:10.1116/1.589035

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

We studied the magnetron ion etching of GaAs in SiCl4/Cl2discharges and sidewall passivation effect which closely relates to the anisotropic dry etching. The effects of a variety of process parameters on the final via hole profiles and morphologies were also examined. Furthermore, in order to determine the surface chemistry of the residues on GaAs sidewall in magnetron plasmas, surface characterization was undertaken using scanning electron microscopy, transmission electron microscopy combined with an energy dispersive x‐ray spectrometer, and x‐ray photoelectron spectroscopy. It was confirmed that the residues, namely the sidewall protection film, consists of double layers. The aluminum content of the underlayer is four times greater than that of the upper layer. The aluminum mainly results from sputtering of the alumina cathode covers. The formation of the sidewall protection film was identified as the key factor in controlling the via hole profile for GaAs device fabrication.

ISSN:0734-211X    

DOI:10.1116/1.589036

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Etch rates up to 7000 Å/min for InP and 3500 Å/min for GaAs are obtained for high microwave power (1000 W) CH4/H2/Ar electron cyclotron resonance plasma etching. Preferential loss of the group V element leads to nonstoichiometric, unacceptably rough surfaces on In‐based binary semiconductors at microwave powers ≥400 W, regardless of plasma composition. Both Ga‐ and Al‐based materials retain smooth, stoichiometric surfaces even at 1000 W, but the rates are still much slower than for Cl2plasma chemistries. The results suggest that CH4/H2plasmas are not well suited to electron cyclotron resonance systems operating at high powers.

ISSN:0734-211X    

DOI:10.1116/1.589037

出版商:American Vacuum Society    

年代:1996

数据来源: AIP