摘要:

We report a simple fabrication method for suspended submicron silicon and silicon oxide structures. The structures are defined by laser and atomic force microscopy (AFM) writing on a 7-nm-thick aluminum film. For laser writing the minimum obtained linewidth is 500 nm, whereas for AFM it is approximately 100 nm. During AFM writing, aluminum oxide is formed, whereas during laser writing, a compound containing aluminum and silicon is formed. For both processes the nonpatterned aluminum can be dissolved selectively in a wet chemical etch leaving the patterned areas as an etch mask. Alternatively, the aluminum oxide can be etched to form a positive etch mask. Aluminum and aluminum oxide are both excellent etch masks for reactive ion etching (RIE) of silicon and silicon oxide. Hence, by combinations of RIE processes, a variety of structures can be fabricated from the aluminum based masks. To illustrate the flexibility of this technique we demonstrate fabrication of submicron cantilevers and bridges defined in silicon and silicon oxide.

ISSN:1071-1023    

DOI:10.1116/1.590329

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A novel technique is presented to fabricate a silicon submicrometer transmission mask for nanofabrication. One of the applications of the mask is to fabricate a single electron transistor using an ultrahigh vacuum scanning tunneling microscope. The mask fabrication processes involve KOH wet etching, electron beam lithography, low-temperatureSF6/O2plasma-assisted reactive ion etching and focused ion beam techniques. Using this method, we fabricated masks with pattern sizes of2.5×2.5 mm2and opaque parts of submicrometer scale. After the evaporation, by using the mask a submicrometer gap on the metal pattern can be obtained.

ISSN:1071-1023    

DOI:10.1116/1.590330

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Cleaning processes forCHF3reactive ion etched Cu vias, consisting of exposure to a hydrogen plasma, an oxygen plasma, and hexafluoroacetylacetone [H(hfac)] vapors have been investigated. After each step in the cleaning process, the dielectric surface and the Cu surface of via structures were analyzed byin situby angle-resolved x-ray photoelectron spectroscopy. A hydrogen plasma was effective in removing carbon and fluorine deposits on all of the surfaces, and CuO andCu2Oon the Cu surface at the via bottom. It was not effective, however, in removing the Cu deposited on the dielectric surfaces. An oxygen plasma is effective in removing all the carbon and some fluorine deposits. Cu deposits on the dielectric surfaces were not removed, however, and the Cu surface was oxidized. Exposure to H(hfac) vapors reduced some of the Cu deposits on the dielectric, however Cu diffusion intoSiO2possibly occurred during this exposure at the elevated temperature of 200 °C. CuO andCu2Owere removed by the H(hfac) exposure above 150 °C. A three-step cleaning sequence was devised which consists of a brief oxygen-plasma exposure, a dilute-HF solution dip, followed by exposure to H(hfac) vapors. The cleaning sequence is effective in obtaining a clean dielectric surface and an oxide-free Cu surface at the via bottom that allows low contact resistances of5.8–6.8×10−11 Ω cm2.

ISSN:1071-1023    

DOI:10.1116/1.590331

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Mass spectroscopy is used to characterize the endpoint uniformity of silicon dioxide etching in an electron cyclotron resonance (ECR) plasma etch process. Etch products are observed using a two stage differentially pumped mass spectrometry system attached to the ECR process chamber. Specifically, usingCF4andD2etch gases, the partial pressure of CO-containing etch products decays near the endpoint, and the rate of signal decay is directly correlated with the uniformity determined from optical interferometry thickness measurements. To correlate the mass spectrometer signal with the etch rate variation across the wafer, etch uniformity is altered by changing the ECR electromagnet geometry and by modifying the initial oxide uniformity. ACOF2etch product material balance is developed to model the observed concentration versus time data, resulting in a quantitative correlation between change in endpoint slope and uniformity. The ability to utilize a process-state sensor, such as a mass spectrometer, for wafer-state information will result in new approaches for sensing, optimizing, and controlling integrated circuit fabrication processes.

ISSN:1071-1023    

DOI:10.1116/1.590332

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

BCl3reactive ion etching for gate recessing of GaInP/InGaAs/GaAs pseudomorphic high electron mobility transistors (PHEMTs) is found improved by the addition of an appropriate amount of Ar to the gas flow. The influence of theBCl3/Argas flow ratio on GaAs to GaInP etch selectivity, surface roughness, and surface damage was studied. The results indicate that the conditions for minimum plasma damage, as determined by photoreflectance (PR) spectroscopy, corresponded with the conditions for minimum surface roughness, as determined by atomic force microscopy (AFM). The optimalBCl3/Argas flow ratio for minimum surface damage and roughness was found to be 6:4. TwoBCl3:Arflow rate ratios, 6:4 (optimal ratio) and 10:0 (pureBCl3)were used for gate recess etching in the fabrication of GaInP/InGaAs/GaAs PHEMTs. From drain–source current to gate–source voltage(Ids–Vgs)measurements, it was found that the plasma-induced damage for the sampleScdry etched with 6:4BCl3/Aris less than that of the sampleSedry etched with pureBCl3.The dc and small signal rf characteristics of PHEMTScwere superior to those of the wet-etched PHEMTS0and PHEMTSedry etched with pureBCl3.The improvement is attributed to the lower parasitic source resistance associated with the tighter recess geometry of theBCl3plasma recess device. These results show that photoreflectance spectroscopy is a powerful tool for investigating surface damage and can be used to improve the performance of PHEMTs.

ISSN:1071-1023    

DOI:10.1116/1.590369

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The process known as ionized physical vapor deposition, or I-PVD, consists of the physical sputtering of metal atoms into a dense, inert gas plasma, ionization of the sputtered metal atoms, and subsequent deposition of the films from these metal ions. Measurements have shown a decrease in electron temperature coupled with an unexpected decrease in plasma density as a function of increasing metal flux. Recent plasma modeling work has suggested gas rarefaction as the underlying factor in these declines. Measurements of neutral gas density in the plasma region reported here confirm this model and are consistent with earlier studies of sputtered atom induced gas heating and rarefaction.

ISSN:1071-1023    

DOI:10.1116/1.590333

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We have observed atomically flat gold surfaces deposited on Si (111) 7×7 surfaces. These films are deposited by conventional evaporative deposition at a pressure below2×10−6 Pa.The surface topography was taken by scanning tunneling microscopy. Atomically flat terraces as large as 100 Å separated by steps were observed. This surface should provide a good substrate for scanning tunneling microscopy studies.

ISSN:1071-1023    

DOI:10.1116/1.590334

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Cu metal organic chemical vapor deposition has been performed on TiN/Si(100) substrates using Cu(I)(hfac)(vtms) at various substrate(110⩽Ts⩽300 °C)and bubbler temperature(0⩽Tb⩽30 °C)conditions, in which the early stage of film formation characterized by scanning electron microscopy andin situlaser beam(λ=6328 Å)reflectance measurement could be well correlated with the surface roughness and the electrical resistivity of the copper films developed in a later stage. All the reflectance versus deposition time curves showed a qualitatively similar shape consisting of three sequential parts: a rapid initial decrease to a minimum, an increase to a maximum, and a gradual decay to almost zero, in which the minimum and maximum roughly correspond to the onset and completion of island coalescence, respectively. As theTsis raised and/or theTbis lowered, larger islands were formed in a smaller density at the onset of island coalescence due to a lower nucleation rate. The surface roughness gradually develops with increasing film thickness after forming a continuous film, but it does not saturate at a thickness of ∼2 μm and shows a correlation with the average island size in the earlier coalescence stage, i.e., the smaller islands evolves to a smoother surface. Above the threshold temperature(Ts∼230forTb=30 °C)the copper islands begin to show facets and at even higherTslarge truncated polyhedron-shaped copper islands are formed, which upon coalescing leave many interfacial voids to result in a film with a very rough surface and a high electrical resistivity. The copper films deposited at150⩽Ts⩽200 °Chave a very low value ofρ≈2 μΩ cm,which increases by a factor of ∼2 whenTsis lowered to 110 °C. The latter was accompanied by the formation of smaller islands at the onset of coalescence, and therefore the increase in ρ atTs⩽150 °Cwas attributed to the electron scattering at the grain boundaries.

ISSN:1071-1023    

DOI:10.1116/1.590335

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Passivation layers of 200 Å sputtered Cr–O as well as reactive sputtered Cr–N–O were studied with respect to the passivation capability against thermal oxidation of Cu in flowing nitrogen and flowing oxygen ambients. In a flowingN2ambient, both Cr–O and Cr–N–O passivation layers were able to prohibit oxidation of Cu at temperatures up to 700 °C. In anO2ambient, the passivation capability of Cr–N–O layer was found to be 500 °C, which is 150 °C higher than that of Cr–O layer. The superiority of the passivation capability of the Cr–N–O layer is presumably due to decoration of the surface defects and grain boundaries with nitrogen, which provide fast paths for oxygen and copper diffusion.

ISSN:1071-1023    

DOI:10.1116/1.590336

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The microstructural, optical, and electronic characteristics of both Cl-doped ZnMgSSe epilayers and Schottky diodes grown by the molecular beam epitaxy method onn+-type GaAs (100) substrates with different thicknesses of Cl-doped ZnSe buffer layers were investigated via three measurements: transmission electron microscopy, photoluminescence, and deep level transient spectroscopy. The V-shaped stacking faults, originating at or near the ZnSe:Cl (buffer layer)/GaAs interface and extending into the ZnMgSSe:Cl epilayer, were discovered to have the evident inclination to exist in samples with thicker ZnSe:Cl buffer layers and higher growth temperatures. Evidence also revealed that the stacking faults not only produced poor optical quality of ZnMgSSe:Cl thin film, but also created more interface state densities at theAu/n-type ZnMgSSe:Cl Schottky junction. Such results are the main factors to damage theI–Vcharacteristics ofAu/n-type ZnMgSSe:Cl Schottky diode, including the less forward conduction current density, the bigger turn-on voltage, and the larger reverse leakage current followed by the smaller reverse breakdown voltage.

ISSN:1071-1023    

DOI:10.1116/1.590337

出版商:American Vacuum Society    

年代:1998

数据来源: AIP