摘要:

The inherent potential of molecular beam epitaxy (MBE) has been exploited to grow large area slices of low defect density GaAlAs/GaAs heterostructures to fabricate several semiconductor guided wave devices. Passive rib waveguides had losses of<2 dB cm−1. Phase modulators exhibited a π phase shift for an applied bias of 9 V, internal losses of less than 2.5 dB with a modulation capability to l.2 GHz. Directional couplers fabricated from the same material exhibited a switching voltage of 16 volts and an extinction ratio better than 14 dB. The MBE growth procedure is outlined and the steps critical to the subsequent successful fabrication of guided wave devices are discussed.

ISSN:0734-211X    

DOI:10.1116/1.583108

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

A summary of the results of a few experiments on a variety of structures based on GaAs–AlGaAs heterojunctions, in which the AlGaAs was Si doped are reported. RHEED and SIMS results are presented for heavily and moderately doped AlGaAs, showing that Si segregated toward the growing front. Photoluminescence spectra of heavily doped AlGaAs has a dominant low energy peak and is absent of the exciton peak. Normal and inverted selectively doped structures were grown at a variety of conditions. Their properties demonstrate that Si segregates toward the growing front, and suggests that this effect could be the main cause of the low mobility in inverted structures.

ISSN:0734-211X    

DOI:10.1116/1.583110

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

In0.53Ga0.47As and InP were grown on InP substrate by using dimeric molecules of arsenic and phosphorus. A Riber cracker cell and a laboratory designed gas cell were used. Cracking rate inside the two kinds of cells was studied by a modulation beam mass spectrometry technique (MBMS). Cracking rate up to 95% was obtained for the gas cell. The ratioM2/M4in the flux reaches 103. The use of As2species for In0.53Ga0.47As growth allows a saving of arsenic compared with As4species. A reduction of the incorporation rate of carbon is observed. Photoluminescence efficiency is increased by a factor of 5. PIN photodiodes exibit low dark current down to 25 nA at−10 V in As2grown InGaAs, 103less than in As4grown ternary material, on mesa diameter of 170 μm. We describe growth conditions of InP by using cracker cell and gas cell as phosphorus sources. Gas source seems to be a promising phosphorus source due to its large autonomy and hydrogen pressure which favors PH3recombination and impurities reduction.

ISSN:0734-211X    

DOI:10.1116/1.583111

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

The high‐temperature behavior of TiSi2films, deposited on a polygate structure, was studied by means of Auger electron spectroscopy and low‐energy ion scattering. Both techniques reveal that upon heating at temperatures in excess of 600 °C the surface of the silicide film becomes Si‐enriched to an extent corresponding to TiSi4. This observation is in qualitative agreement with the theory of surface segregation, which predicts enrichment of the element with the lowest heat of vaporization. However, the effect is found not to be restricted to the topmost atomic layer, but extends to a depth of 30–40 Å. With oxygen, introduced into the vacuum system to a level of 10−6–10−4Torr, the same amount of enrichment is obtained, now at 500–600 °C. In this temperature range Ti desorbs from the silicide as TiOx.Apart from the outer surface layer the silicide is not oxidized under these circumstances. At higher temperatures, around 800 °C, this reactive adsorption–desorption of oxygen does not result in the formation of a thicker oxide layer but leads to a decomposition of the silicide. The attendant loss of Si and Ti, as measured with Rutherford backscattering, causes a severe roughening of the film surface.

ISSN:0734-211X    

DOI:10.1116/1.583112

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Polycrystalline TaSi2thin films were prepared by furnace reaction of ion beam sputtered tantalum layers with silicon surfaces. X‐ray diffraction measurements indicate that the films are single phase hexagonal disilicide. Impurity levels are at or below the detection limits of Auger spectroscopy. The samples exhibit a room temperature intrinsic resistivity of ∼40 μΩ cm and a residual resistivity component as low as 4 μΩ cm. The Hall coefficient is negative, giving an apparent electron concentration of 6.5×1022cm−3at room temperature. A representative carrier mobility of 58 cm2/V s at room temperature (obtained from geometrical magnetoresistance measurements) was much larger than the Hall mobility (1.9 cm2/V s), suggesting multicarrier effects. The galvanomagnetic properties can be described by the equations for two degenerate, isotropic bands and be given a physical interpretation similar to that of Mott’ss‐dscattering model. However, it is emphasized that the two‐band model is likely only a crude approximation for transition metals and their compounds. A two‐layer model shows that in certain instances the apparent transport properties of the films are due to the silicon substrate.

ISSN:0734-211X    

DOI:10.1116/1.583113

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Refractory metal silicide/poly‐Si composites are replacing poly‐Si in VLSI circuits in order to reduce runner resistance without sacrificing poly‐Si MOS compatibility. In a typical integrated circuit (IC) fabrication sequence, the gate serves as a mask for the formation of self‐aligned sources and drains. It is, therefore, exposed to various heavy implants of B, P, or As. These implants subsequently redistribute during further processing. This paper investigates the effect of dopant implantation and redistribution on the mechanical, structural and electrical properties of silicided poly‐Si. Implantation increases the sheet resistance of 2500 Å of sintered TaSi2by a factor of 2–3. This coincides with a decrease in the silicide stress, proportional to the implant range in TaSi2, and to a lesser degree, the implant dose. These stress changes, however, recover by 500 °C, while the TaSi2resistivity returns to its nominal value (2–2.5Ω/⧠) following a 900 °C heat cycle. Doses as high as 1E16As/cm2do not render TaSi2amorphous. If the underlying LPCVD poly‐Si is initially undoped, the nature of the impurity appears to influence subsequent poly‐Si recrystallization. With P/As, the poly‐Si grains grow during a high temperature anneal. However, with B, the grains remain needle‐like. This recrystallized poly‐Si grain structure is nevertheless significantly different from the large, equiaxed grains developed when the poly‐Si is doped in a PBr3gas flow, prior to TaSi2deposition.N‐type impurities readily redistribute from the silicide into poly‐Si by 950 °C. Thus, a singlen+source/drain implant can effectively dope the gate, buried gate‐substrate contacts and junctions in NMOS circuits. The corresponding gate metal work function φmis comparable to the reported values forn+poly‐Si. B, on the other hand, is retained in the silicide. This results in a somewhat lower φmvalue than expected forp+poly‐Si.

ISSN:0734-211X    

DOI:10.1116/1.583114

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

A new angled‐surface‐moving model for surface planarization by rf bias sputtering is proposed. This planarization is achieved by angular selective etching of SiO2films on top of metal stripes. A two‐step rf bias‐sputtering technique was developed, based on the new model. In this technique, the substrate bias voltage was changed in two steps during bias sputtering. The first step was to fill gaps without microcracks. The second step was to planarize at higher substrate bias. The planarized SiO2layer surface, deposited on thermally oxidized Si wafers with Mo stripe patterns, had good flatness. A planarized 4‐level metallization test structure was fabricated by the two‐step rf bias‐sputtering.

ISSN:0734-211X    

DOI:10.1116/1.583116

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

A low‐pass frequency filter model for predicting thickness variations on complex topography is investigated for several spin‐coated thin films. Frequency weighting parameters are presented for PMMA, HPR204, HPR206, OFPR800, MPR resist coatings and a spun‐on glass coating (X‐600). One weighting parameteratends to be inversely proportional to the solution viscosity and indicates the conformality of the coating. The other parameter Pmindepends on the spun‐on film thickness and the step height. Simulated coated topography contours are compared to experimental profilometer traces to demonstrate the validity of the modeling technique. Effects of topography orientation with respect to the wafer center are also examined. More uniform spun‐on coatings on topography are obtained at lower spin speeds. PMMA and HPR206 coatings are compared. Simulations of two‐ and three‐dimensional coated topography are presented to indicate coating thicknesses variations within complex arrays and at the edge of large arrays.

ISSN:0734-211X    

DOI:10.1116/1.583117

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Two layer resist systems for hybrid e‐beam/deep‐UV lithography are described which consists of positive type RE5000P (Hitachi Chemical) or negative type CMS‐EX (Toyo Soda) and PMMA. The systems have no interfacial problems between the top layer resist and the bottom layer resist. The thin RE5000P and CMS‐EX have very high UV absorption coefficients below 250 nm and form a high contrast mask for optical pattern transfer to the thick PMMA layer. The sensitivity of these systems for e‐beam lithography is 1 μC/cm2(RE5000P/PMMA) and 2.5 μC/cm2(CMS‐EX/PMMA) which are one order of magnitude higher than the sensitivity of the AZ1350J/PMMA system. High image resolution and linewidth control with reduced proximity effects have been demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.583118

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

An electron beam (EB) prober for VLSI internal diagnosis has been developed. The essential requirements for an EB prober are quantitative voltage measurement, waveform observation with high time resolution, and a diagnostic function for locating faults easily. The newly developed EB prober satisfies these requirements. It has an improved energy analyzer for quantitative voltage measurement, a stroboscopic function with 1 ns time resolution, and a unique diagnostic function wherein voltage images of LSIs are compared. This voltage image comparison provides easy detection of faulty areas by comparing voltage images of both faulty and normal LSIs. In this respect this EB prober is the first machine which considers locating faults easily in a large VLSI chip.

ISSN:0734-211X    

DOI:10.1116/1.583075

出版商:American Vacuum Society    

年代:1985

数据来源: AIP