摘要:

We have shown that a discharge can be sustained at low pressure (≲10−3Torr) in a single‐wafer reactor using experimental quarter‐wave helical resonator structures operated at radio frequencies. These discharge sources have been used to etch submicron‐wide polysilicon gates with chlorine and chlorine/oxygen mixtures. Selectivities for undoped polysilicon over oxide and hard baked trilevel photoresist were 70:1 and 2.8:1, respectively, in a 75 W discharge operated at 0.1 mTorr with a Cl2/1% O2feed gas mixture. Anisotropic profiles of 0.25 μm lines were obtained across 100 mm wafers with negligible linewidth loss. These preliminary experiments show that rf resonator discharges may offer an alternative to low‐pressure microwave discharges such as those based on electron cyclotron resonance.

ISSN:0734-211X    

DOI:10.1116/1.584859

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Plasma etch rates of both aluminum and photoresist masked polysilicon and silicon nitride are reported. Both thermally grown and plasma deposited substrates of both films were studied. It is shown that all aluminum masked substrates except thermal nitride exhibit enhanced etch rates relative to photoresist masked samples. Aluminum masked thermal nitride etches more slowly than does photoresist masked. These results are shown to be consistent with a metal catalyzed surface reaction which generates additional fluorine radicals at the surface of the wafer.

ISSN:0734-211X    

DOI:10.1116/1.584829

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

The rapid thermal oxidation (RTO) technique has been physically and electrically evaluated on single crystal and amorphous silicon (α‐Si). Data on interface width, oxidation kinetics, and recrystallization kinetics as well as the conduction characteristics are reported for oxidized amorphous silicon. Our results indicate the RTO oxide grown on amorphous silicon is a film with peculiar behavior. By the use of a 250 Å thick oxide, no Fowler–Nordheim conduction is activated at ∼5 MV/cm, and no evidence of conduction is registered until a field of 6 MV/cm (breakdown field). The point‐to‐point film thickness uniformity results are better than that obtained from furnace oxidation on polysilicon. We suggest this to be related both to α‐Si used as a starting material, and to the short oxidation time. A special double metal capacitor test has been proposed and successfully used in order to study the electrical characteristics without any drawback on sample morphology. Based on our experimental results we consider RTO on amorphous silicon as a suitable technique to be used in multipolysilicon device application.

ISSN:0734-211X    

DOI:10.1116/1.584857

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

A retrospective view of several hundred epilayers provides an insight into the factors relating to molecular‐beam epitaxy (MBE). The major source of particulates was found to be associated with the high electron flux in the deposition region of the MBE system, coming from the electron beam evaporator, and with the unstable excess Si deposits in the growth chamber. Reduction of Si accumulation in the deposition zone by containment of the Si flux significantly reduces particulate densities in epilayers. Voltages applied to a tantalum plate, situated adjacent to the growth flux zone, affected particulate densities in the epilayers confirming that a significant percentage of the particulate contamination is derived from charge effects. Other factors affecting the particulate contamination of the epilayer include the stability of the electron beam evaporator, the substrate rotation mechanism, and the method of evacuation of the load lock when transferring the samples into vacuum. Two types of particulate‐related features have been identified. The first type thought to be due to microscopic particulates is decorated by crystallographic defects, whereas the second type, which is free of these defects, appears to be related to shadowing of growth by larger particulates. A correlation in the densities of both types of particulate defects in epilayers grown under a variety of experimental conditions suggests a common source.

ISSN:0734-211X    

DOI:10.1116/1.584860

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

We use thermally evaporated fluoride films as dry etch masks to fabricate sub‐100 nm wide features into III–V heterostructures. Fluorides are compatible with lift‐off processing and display excellent resistance to halide etch gas mixtures. Among the advantages which these materials offer over conventional metal masks are their thermal stability, good adhesion, high resistivity, the avoidance of ‘‘flags’’ arising from angle evaporation, and the ease with which they can be removed from the surface. By adjusting the composition of these fluorides and thereby controlling their grain size, we can optimize the resolution and erosion rates of our masks and fabricate structures with lateral sizes below 20 nm.

ISSN:0734-211X    

DOI:10.1116/1.584861

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Different samples of poly(trifluoro‐2,2,2 ethyl methacrylate), made either by radical or by anionic copolymerization, with molecular weights ranging from 100 000 to 700 000 g mol−1have been investigated as positive x ray and electron resist. The best sensitivity and contrast have been found for the sample with the lower polydispersity index and the higher molecular weight in optimized developing conditions. Furthermore, we have found that in optimized developers, the ratio of molecular weights before and after irradiation, with a dose corresponding to the total dissolution of the film, is nearly a constant. The best resolution (0.5 μm for line and space gratings in a film of 0.6 μm thickness) has been obtained when development is carried out at low temperature (5 °C) in an appropriate solvent–nonsolvent mixture.

ISSN:0734-211X    

DOI:10.1116/1.584862

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Large‐area (cm2) proximity patterning of selected microelectronic polymers using soft vacuum (0.05 Torr) pulsed electron beams is described using polymers with widely differing electron sensitivities (2–80 μC/cm2at 20 keV). The short duration (∼100 ns) electron beams are produced in the pulsed mode (25–28 keV electrons, 2–3 J/pulse). These electrons impinge upon thin polymer films in the presence of an ambient gas to produce electron initiated bulk polymer chemical reactions including partial self‐development. In soft vacuum, pulsed electron beams are shown to be capable of transferring submicron (∼0.5 μm) features from an electron transmitting stencil mask onto poly(methylmethacrylate) (∼3 μm thick) films. Wide‐area exposure (field size ∼20 mm) is also demonstrated for micron feature sizes. Soft vacuum lithography appears well suited to microelectronics packaging lithography where resist thickness is substantial, linewidths are 1–10 microns, areas to be processed are large (100 cm2), and where registration requirements are not so critical.

ISSN:0734-211X    

DOI:10.1116/1.584863

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

This paper presents the high‐aspect‐ratio pattern fabrication method for KrF excimer laser lithography. The alkaline surface treatment of a resist before exposure can enhance the contrast of a conventional naphthoquinone‐diazide‐based deep UV positive resist. It has been found that the improvement depends upon the structure of the resist. High‐aspect‐ratio sub‐half‐micron patterns of the deep UV resist with an easy azo‐coupling reaction were successfully attained using this simple method without compromising sensitivity.

ISSN:0734-211X    

DOI:10.1116/1.584864

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

This paper describes a mask‐to‐wafer alignment technique for submicron x‐ray lithography. A new gap and lateral alignment method is proposed to avoid the interference of lateral displacement on the gap detection signal and to accurately detect lateral displacement in the wide gap range. This method utilizes a pair of marks: a single grating, which does not have a grating acting as a mark on the wafer, and double‐pitch dual gratings, whose wafer grating pitch is twice as large as the mask grating pitch. Gap detection is performed using an interference signal and an envelope signal. The interference signal is produced by superimposing a positive first‐order diffraction light beam reflected from the mask grating and that of the wafer surface. The envelope signal makes it possible to set an absolute gap. The linear part of the interference signal is used for precision servocontrol at the gap setting point. The lateral alignment, on the other hand, is performed using the intensity difference between positive first‐order and negative first‐order diffraction lights generated by the double‐pitch dual gratings. A highly sensitive and stable lateral displacement detection signal is obtained at the specific gap. The signal has a triangular waveform and hardly varies for gap fluctuations of a few microns from the specific gap. The gap range where a stable signal can be obtained, is 50 times larger than that of the conventional dual grating method. These experimental results agree quite well with theoretical calculations. By combining the single grating method and the double‐pitch dual grating method, accuracies of ±0.02 μm in both gap and lateral alignment servocontrols are realized.

ISSN:0734-211X    

DOI:10.1116/1.584865

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

GaSb (001) surfaces were prepared by molecular‐beam epitaxy. Auger electron spectroscopy (AES) and electron energy‐loss spectroscopy (EELS) are reported for clean surfaces exposed to oxygen, and during the process the ionization gauge of the vacuum system is turned on. Successive stages of chemisorption can be distinguished. For oxygen coverage up to 0.5 monolayer, the surface states are saturated by bonding of the oxygen with Ga and Sb atoms. Sb atoms desorb causing significant Sb depletion in the first layer. Larger exposures further increase the coverage and induce, in the EELS spectra, losses related to O(2p) and O(2s) atomic states and new plasmon excitations. In the AES spectra the shift of Auger emission lines which are characteristic of Sb and Ga oxide forms appear; at coverages of about one monolayer back bonds break forming Sb2O3and Ga2O3. Further exposures to oxygen result in thicker oxide layers of Ga and Sb.

ISSN:0734-211X    

DOI:10.1116/1.584830

出版商:American Vacuum Society    

年代:1990

数据来源: AIP