摘要:

Laser‐induced damage in optical coatings is generally associated with micrometer‐scale defects. A simple geometric model for nodule‐shaped defects is commonly used to describe defects in optical coatings. No systematic study has been done, however, to prove the applicability of that model to an optical coating deposition process. Not all defects have a classic nodule geometry. The present study uses atomic force microscopy (AFM) and scanning electron microscopy to characterize the topography of coating defects in a HfO2/SiO2multilayer mirror system. Focused ion‐beam cross sectioning is then used to study the underlying defect structure. This work develops a model for defect shape such that the overall geometry of a coating defect, particularly the seed size and depth, can be inferred from nondestructive evaluation measurements such as AFM. The relative mechanical stabilities of nodular defects can be deduced based on the nodule’s geometry. Auger analysis showed that the seed material that causes nodular defects in HfO2/SiO2multilayers is a hafnia oxide. Such characterization capabilities are needed for understanding the enhanced susceptibility of particular defects to laser damage and for developing improved techniques for depositing low‐defect density coatings.

ISSN:0734-2101    

DOI:10.1116/1.578948

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Thermal desorption spectroscopy (TDS), along with Auger electron spectroscopy, was used to study the desorption of H2and CO from baked 304 and 347 stainless‐steel samples exposed only to residual gases. Both 347 and 304 samples gave identical TDS spectra. The spectra for CO contained a sharp leading peak centered in the temperature range 410–440 °C and an exponentially increasing part for temperatures higher than 500 °C, with a small peak around 600 °C appearing as a shoulder. The leading peak followed a second‐order desorption behavior with an activation energy of 28±2 kcal/mol, suggesting that the rate‐limiting step for this peak is most likely a surface reaction that produces the CO molecules in the surface layer. The amount of desorbed CO corresponding to this peak was ∼0.5×1014molecules/cm2. The exponentially rising part of the CO spectrum appeared to originate from a bulk diffusion process. The TDS spectrum for H2consisted of a main peak centered also in the temperature range 410–440 °C, with two small peaks appearing as shoulders at ∼500 and 650 °C. The main peak in this case also displayed a second‐order behavior with an activation energy of 14±2 kcal/mol. The amount of desorbed H2, ∼1.9×1015molecules/cm2, appeared to be independent of the concentration of hydrogen in the bulk, indicating that the majority of the desorbed H2originated from the surface layer.

ISSN:0734-2101    

DOI:10.1116/1.578949

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Amorphous carbon and hydrogen containing amorphous carbon films have been prepared by evaporating polycrystalline graphite in hydrogen‐free atmosphere (pH2<10−8mbar) and in the presence of hydrogen at different pressures (3×10−4–1.7×10−2mbar), respectively. After deposition, the films have been characterized byinsituphotoelectron spectroscopy. The composition of the gas phase during graphite evaporation in the presence of hydrogen was measured with a quadrupole mass spectrometer. The gas phase data have been correlated to the hydrogen content in the film. It is found that hydrogen is incorporated preferably into amorphous carbon when already bound to carbon in the form of CHx(x=1,2,3) in the gas phase. In addition, the bombardment of a growing amorphous carbon film with high energy hydrogen ions has turned out to be a quite effective means of incorporating hydrogen intoa‐C.  

ISSN:0734-2101    

DOI:10.1116/1.578950

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We study the epitaxial crystallization of a thin film of amorphous Ge deposited at room temperature on Si (111). Silicon surface features which are buried beneath the Ge film are seen to affect the rate of crystallization. In particular, solid phase growth is observed to be enhanced at surface steps and defects in the surface reconstruction. We demonstrate that control of Ge crystallization morphology is possible through manipulation of Si surface structure.

ISSN:0734-2101    

DOI:10.1116/1.578951

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We explore the use of sputtered neutral mass spectrometry (SNMS) for semiconductor and superconductor device processing. SNMS allows us to precisely determine the end point at interfaces during sputter etching of prepatterned semiconductor and superconductor thin films. By postionizing the sputtered neutrals the detection sensitivity is similar for all elements. The dynamic range of up to three orders of magnitude makes precise end‐point detection possible even if the mask allows sputter etching of only a small fraction of the surface of the specimen.

ISSN:0734-2101    

DOI:10.1116/1.578952

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

An insulator figure of merit for an electrostatic wafer holder is introduced. A sputtered Ta2O5membrane has a maximum figure of merit compared to other candidate dielectric coatings, e.g., Al2O3and SiO2. The breakdown strength of sputtered Ta2O5coatings can be optimized by controlling working gas pressure and oxygen concentration: a holding pressure that exceeds 30 gF/cm2(2942 Pa), when 60 V dc is applied in atmosphere. The pressure is not influenced by the duration of the applied voltage. The residual pressure, after voltage is turned off, decreases to 1/50 of initial pressure within 1 s. The breakdown voltage for 60 cm2area wafer holder exceeds ±290 V. A sputtered Ta2O5coating can also be used to smooth relatively rough ceramic substrates. When a polished Al2O3mixed with ZrO2ceramic surface is coated with 10 μm thick sputtered Ta2O5film, good substrate material for an electrostatic chuck is obtained. The sputter rate for the Ta2O5is much larger than that for the Al2O3or SiO2.

ISSN:0734-2101    

DOI:10.1116/1.578953

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Thin films of Pb(MgxNb1−x)Oz(hereafter called PMN) have been deposited on carbon substrate by reactive ion beam sputtering, from a mixed oxide–metal multicomponent target composed of magnesium oxide, and metallic niobium and lead. The substrate temperature and sputtering gas composition (oxygen pressure during deposition) were varied and their effects on the film composition and compositional uniformity were investigated. The major effect seen was the systematic variation in Pb content with changes in temperature and gas composition. We also observed a spatial variation in Pb composition across the substrate and believe this to be caused by film bombardment by argon ions specularly reflected by the target surface. This was supported by results showing a systematic reduction in Pb content in films subjected to secondary ion bombardment during film growth. The selective Pb depletion in PMN films is discussed in terms of various mechanisms found in reactive sputtering environments.

ISSN:0734-2101    

DOI:10.1116/1.578954

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The fluxes of ions and neutral sputtered particles incident at the growth surface during the deposition of TiN by reactive magnetron sputtering from a Ti target in mixed Ar+N2discharges were determined using a combination ofinsitudouble‐modulation mass spectrometry, Langmuir probe, discharge, deposition rate, and film composition measurements. The N2fractionfN2in the discharge was varied from 0 to 1 with the total pressure maintained at 3 mTorr (0.4 Pa). Target nitridation, observed directly through the detection of sputter‐ejected TiN molecules, was found to occur over the narrowfN2range between ≂0.035 and 0.06. WithfN2<0.1, more than 94% of the ion flux incident at the substrate is Ar+while for pure N2discharges, N+2accounts for more than 95% of the incident ions. Both the incident Ar+and N+2ion fluxes are highly monoenergetic with energies corresponding toeVs, whereVsis the applied negative substrate bias with respect to the plasma potential. However, the energy distributions of incident Ti+and N+ions are extended due to the high‐energy tails in their sputter‐ejection energy distributions. The primary sputter‐ejected particles are Ti and N atoms. TiN, TiN+, and Ti+do not contribute significantly to film growth kinetics.

ISSN:0734-2101    

DOI:10.1116/1.578955

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Ni films thinner than 180 nm are deposited on MgO(001) substrates at a temperatureTsof 190 or 280 °C by dc sputtering at 2.5 kV in Ar gas. A dc bias voltageVsbetween 0 and ‐140 V is applied to the substrate during the deposition. A study of structural and physical properties of the Ni film is made by the use of reflection high‐energy electron diffraction (RHEED), cross‐sectional transmission electron microscopy (XTEM), x‐ray reflection diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and by measuring (TCR) in the temperature range from 35 to 135 °C. WhenTs=190 °C the Ni film retains a polycrystalline structure at anyVs. WhenTs=280 °C, asVsincreases from 0 to −140 V the film transforms from the polycrystal to the single crystal with the orientation as Ni(001)∥MgO(001) and Ni〈010〉∥MgO〈010〉, indicating that an optimal value ofVsfor the epitaxial growth ranges from −80 to −110 V. Besides, an analysis of RBS spectra in comparison with XTEM images explains that the atomic density of the Ni film is the highest atVs=−80 V. The optimal condition for the epitaxial growth is also confirmed by the change of TCR as a function ofVs. In conclusion, the epitaxial growth of the Ni film with the lower defect density is dominated atVs=−80 to −110 V by the bombardment of both energetic ions and fast neutrals of Ar to increase the mobility of Ni adatoms and to resputter impurities during the film formation. This effect is pronounced atTs≥280 °C.

ISSN:0734-2101    

DOI:10.1116/1.578956

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Silicon nitride films are prepared by helium‐excited magnetron radio‐frequency sputtering. Excitation energy transfer from He to N2and existence of hydrogenation and oxidation source (O+and OH⋅) in the plasmas are confirmed by optical emission spectroscopy. The structure and characteristics of the resultant films depend on the gas pressure during sputtering: Films produced at pressures above 5 Pa are etched rapidly in a buffered hydrogen fluoride solution and have low refractive indices because their structure is coarse and rich in oxygen and hydrogen or both.

ISSN:0734-2101    

DOI:10.1116/1.578957

出版商:American Vacuum Society    

年代:1994

数据来源: AIP