摘要:

The effect of adding oxygen to a dc discharge containing CF4and NF3, when etching polysilicon, have been studied. It is shown that the increase in atomic fluorine concentration observed in rf discharges is absent in the measurements performed in a dc discharge. This is probably due to the inefficient dissociation of the gas molecules in a dc discharge. This indicates that oxidation reactions in the gas phase are limited. In the dc discharge it is possible to separate several mechanisms that act on the silicon surface. In the case of CF4, the added oxygen helps in keeping the silicon surface clean from polymer formation. This results in an observed maximum in etching rate and yield. For NF3there is no need for a ‘‘cleaning’’ of the silicon surface. The rate and yield decreases monotonically for increasing oxygen concentrations.

ISSN:1071-1023    

DOI:10.1116/1.584532

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The conditions which cause silicon roughening in Cl2RIE plasmas are investigated.Insituellipsometry provides a quantitative interpretation of the extent and nature of the roughening process, while mass spectrometry yields complementary information regarding the composition of the plasma. The degree of roughening is reproducible when base pressures are ≊10−5Torr but is strongly dependent on the rf power and process pressure. Careful selection of these parameters (50 W, 100 mTorr) retains a smooth silicon surface and gradually smooths those which have been roughened. Water vapor has a very significant effect on the etching reactions. In low concentrations it induces roughening and in high concentrations it prevents any etching of silicon. We suggest that silicon oxide micromasks are not responsible for roughening. Instead we propose that hydroxyl (SiOH) groups are the more likely masking species. Roughening of silicon is efficiently prevented when the wafer is patterned with positive photoresist. It is possible that CClx(x=1–4) species can remove the micromasks to retain a smooth surface.

ISSN:1071-1023    

DOI:10.1116/1.584533

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A 0.1‐μm‐gate‐length superconducting field effect transistor (FET) with a coplanar structure is realized by a self‐aligned fabrication process using electron beam lithography. AT‐shaped gate structure with an insulated sidewall makes it possible to form the spacing between the superconducting source and drain electrodes to be<0.15 μm without causing an electrical short. The characteristics of this FET measured at 4.2 K indicate that the superconducting current and normal‐state resistance can be successfully controlled by the applied gate bias.

ISSN:1071-1023    

DOI:10.1116/1.584534

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Highly preferred polycrystalline Si (polysilicon) film growth on amorphous Si with ion‐assisted crystallization by reactive ion beam deposition (RIBD) at the low temperature of 550 °C was investigated. This method uses low‐energy controlled ionized species produced from electron‐cyclotron‐resonance plasma. To achieve highly preferred polysilicon film growth, a new growth process using ion‐assisted crystallization was developed as follows: After a thin amorphous Si film was deposited on an amorphous substrate at 100–150 °C and 100 eV by RIBD using SiH4, it was crystallized at 550 °C by 400‐eV H+and H+2irradiation using the same RIBD system. Then, a polysilicon film was grown at the same temperature and 100 eV by RIBD using SiH4. Polysilicon films grown by this process possess stronger Si(220)‐preferred growth orientation and higher Hall mobility than the films grown directly on amorphous substrates.

ISSN:1071-1023    

DOI:10.1116/1.584535

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Isotopic labeling and step coverage studies of silicon oxide deposited from tetraethoxysilane (TEOS) have been carried out by introducing TEOS(16O) downstream from an18O2discharge. Rutherford backscattering (RBS) data on films deposited near 440 °C show that, on average, one Si–O bond in the original TEOS molecule is preserved in the process, while mass spectrometric results indicate only H216O and C18O16O as gaseous products of the cleavage of the remaining three Si–O bonds. Infrared analyses of films deposited at room temperature show large amounts of Si–OH in a gel‐like material, and the presence of a C■O species. The results suggest a mechanism dominated by diffusion and condensation of Si–OH species that form extensive chains and preserve an Si–16O bond from the original precursor. This is followed by cross‐linking to form the final silicate network; however, Si–O bond cleavage is apparently occurring at potential cross‐linking sites via a carbonate intermediate that promotes isotopic scrambling. Step coverage is shown to be better under conditions (high temperature, low TEOS flow) that favor a low concentration of surface precursors during film growth. This is consistent with the proposed mechanism since second‐order condensation reactions of surface species under these conditions would be kinetically limited allowing effective mean free paths to increase dramatically. Experimental parameters and techniques, such as modulated chemical feeds to enhance the role of surface migration also lead to improved step coverage. However, we also conclude that perfectly conformal coverage based on similar mechanisms will inevitably lead to void formation in high‐aspect‐ratio topography because of transport limitations.

ISSN:1071-1023    

DOI:10.1116/1.584536

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The etch rates of Si3N4, SiO2, and doped polycrystalline silicon with CF4plasmas have been examined as a function of O2dilution and radio frequency (rf) (13.56 MHz) power density at constant residence time (25 mTorr and 25 sccm total process gas flow rate) at 22±2 °C in a batch reactor. At fixed reactor pressure and process gas composition, the etch rates of these materials increase linearly, with different slopes, with increasing rf power density. Under the conditions studied, the etch rates of SiO2are lower than those of the other two materials and are primarily a function of rf power for CF4plasmas that are diluted with 0%–25% O2by flow rate. In comparison, the etch rates of Si3N4and doped polycrystalline silicon are functions of both rf power density and gas composition, although at each rf power level (200, 300, and 400 W) the Si3N4etch rate reaches a plateau at an O2dilution of ∼10%–15% by flow rate. Although the doped polycrystalline silicon etch rate exhibits similar behavior at 200 and 300 W, a steady increase in etch rate is noted at 400 W over the range of O2dilution examined in this work. At low O2dilutions, the Si3N4etch rate is greater than the doped polycrystalline silicon etch rate. However, with increasing O2dilution, the doped polycrystalline silicon etch rate exceeds the Si3N4etch rate, with the intersections of these etch rate curves shifting to greater O2dilution at higher rf power settings.

ISSN:1071-1023    

DOI:10.1116/1.584537

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The RHEED specular beam profiles produced by GaAs vicinal surfaces are examined and correlated with the surface topography. It is found that the shape of split peaks produced with the incident beam normal to step edges is a measure of surface orientation over lengths on the order of terrace widths, but is not sensitive to short range roughness on the terraces themselves. The profile produced with the incident beam parallel to step edges is sensitive to terrace roughness and can be correlated with RHEED intensity oscillation behavior. It is also found that reconstruction disorder can influence the specular beamwidth.

ISSN:1071-1023    

DOI:10.1116/1.584538

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A formalism is developed using the effective mass approximation to evaluate the density of states of quasi‐two, ‐one, and ‐zero dimensional semiconductor superlattices (QnD SLs). This formalism is applied to GaAs/AlGaAs systems to determine the effect of barrier size on the density of states. The calculated results show that the density of states of QnD SLs evolves from that of QnD structures to that of Q(n+1) D structures with decreasing barrier sizes, wheren=0, 1, and 2.

ISSN:1071-1023    

DOI:10.1116/1.584539

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The high optical density of the conventional positive resist in the deep UV region (190 nm to 300 nm) prevents its use in the fabrication of high contrast patterns. The photobleachable deep UV resist composed of a 1,3‐dicarbonyl‐2‐diazo compound as the alkaline dissolution inhibitor and an alkaline‐soluble styrene polymer as the resin matrix, which we developed, is one promising approach to resolve these problems. Using this resist, high contrast 0.5 μm patterns were obtained with a KrF excimer laser stepper. In this paper, we have applied photoacid generators to such photobleachable resists. The photoacid generator used was triphenylsulfonium hexafluoroarsenate, and it greatly enhanced the sensitivity and contrast of the resist. The decomposition of diazo compound in the resist was significantly enhanced (and the dissolution characteristics improved) in the presence of the onium salt. This novel positive resist utilizing chemical amplification more than meets the requirements for KrF excimer laser lithography.

ISSN:1071-1023    

DOI:10.1116/1.584540

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.584541

出版商:American Vacuum Society    

年代:1989

数据来源: AIP