An enhanced sensitivity null ellipsometry technique for studying films on substrates: Application to silicon nitride on gallium arsenide

Alterovitz, Samuel A.; Bu-Abbud, George H.; Woollam, John A.; Liu, David C.

doi:10.1063/1.332137

Cited by 21 publications

(9 citation statements)

References 13 publications

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“…The electron density or index of refraction of Si(CH 3 ) 3 , which is used to “attach” the monolayers to the substrate, is nearly the same as SiO 2 . , Hence, with chemisorbed Si(CH 3 ) 3 the X-ray analysis includes the methyl groups as a part of the monolayer. This marks a difference between the monolayer film thickness and the average thickness of the multilayer film of ∼1 Å . For a thick film the contribution of the Si(CH 3 ) 3 is minimal.…”

Section: Resultsmentioning

confidence: 99%

“…Ψ cal and Δ cal are calculated for the multilayer model using known optical parameters for the substrate, SiO 2 film, and ambient vapor and allowing n , k , and h for the LB film to vary. Ψ cal and Δ cal are then fit to the experimental values of Ψ and Δ using a regression analysis to minimize the mean-square error . Measurements at multiple angles assure an overdetermined system and reliable evaluation of n , k , and h .…”

Section: Resultsmentioning

confidence: 99%

“…Ψ cal and ∆ cal are then fit to the experimental values of Ψ and ∆ using a regression analysis to minimize the mean-square error. 27 Measurements at multiple angles assure an overdetermined system and reliable evaluation of n, k, and h. The LB film was treated as a homogeneous layer. Indeed, further subdivision of the LB film into deposited layers was not possible even with the highest quality data we obtained.…”

Section: Resultsmentioning

confidence: 99%

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Polar Polymeric Langmuir−Blodgett Films for Optical Applications

et al. 1997

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A side-chain liquid crystalline copolymer containing ether−nitrobiphenyl groups was investigated as a nonlinear optical material. Ultrathin films have shown second harmonic generation and therefore have a variety of interesting applications. Waveguides composed of multilayers of the copolymer have been fabricated, and propagation losses as low as 2.3 dB/cm in a lowest order TE mode at 800 nm wavelength have been measured. The second harmonic coefficient is d 33 = 42.0 ± 1.7 pm/V at the 1064 nm fundamental wavelength and is consistent with an oriented gas model. From spectroscopic ellipsometry measurements the film refractive index is 2.24 ± 0.15 and the extinction coefficient ≤0.05 in the visible range of wavelengths. The monolayer and multilayer repeat structures were also studied by X-ray reflectivity and diffraction. The optical thickness and the oscillations in the reflectivity were in reasonable accord with a repeat length of about 3.6 nm.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Polar Polymeric Langmuir−Blodgett Films for Optical Applications

et al. 1997

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“…More details about sample preparation are in Ref. (2 and 7).Ellipsometry was performed using a rotating analyzer ellipsometer with a laser or a Hg arc lamp light source.The multiple angles of incidence and wavelengths method was used in the data analysis (8,9). This method gives a unique determination of the refractive index and the extinction coefficient at each wavelength, and the thickness of the film, without an assumption on the composition of the film, or a prior knowledge of the thickness.…”

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confidence: 99%

Ellipsometric and Optical Study of Amorphous Hydrogenated Carbon Films

Alterovitz

Warner

Liu

et al. 1986

J. Electrochem. Soc.

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A low-frequency plasma deposition system was used to prepare amorphous hydrogenated carbon (a-C;H) films. The growth energy was varied by changing the power and/or pressure of the plasma. Ellipsometry and optical absorption were used to obtain the optical energy gap, the density of states, and the refractive index. Ion sputtering was used in conjunction with ellipsometry and Auger electron spectroscopy to get absolute sputtering rates. The plasma deposited a-C:H is amorphous with optical energy gap of approximately 2.0-2.4 eV. These a-C:H films have higher density and/or hardness, higher refractive index, and lower optical energy gaps with increasing energy of the particles in the plasma, while the density of states remains unchanged. These results are in agreement and give a fine-tuned positive confirmation to an existing conjecture on the nature of a-C:H films (1).Insulator films on semiconductors have a wide variety of applications, including passivation, insulation, capping, etc. In the case of silicon, the silicon based films SiO2 and Si3N4 have been successfully used for all the required applications. However, the need for high-speed devices and integrated circuits requires the use of Group III-V semiconductor devices and substrates. SiO~ and Si3N4 proved to be inadequate for some of these applications for Group III-V semiconductors. Thus, new types of insulator films for one or more of the required applications are needed. In this study we have chosen a-C:H for the insulator film. Some of the attractive properties of a-C:H are: (i) it is easily prepared as a homogeneous film (2): (it) it is very hard mechanically and chemically: (iii) it has a high breakdown voltage (3) and resistivity: (iv) it has a relatively low interface density of states on Si (4) and InP (3): (v) it has a variable energy gap (1, 5); and (vi) it can be used in metal-insulator-metal (MIM) structures (6).However, not all the desirable properties are achieved in a single sample, i.e., the highest energy gap sample will have a rather low mechanical hardness (1). It was suggested in Ref.(1) that the growth energy environment controls the energy bandgap, the hardness, the hydrogen concentration, and bond type. Thus, it may not be possible to optimize all the desirable parameters simultaneously. This conjecture was made using samples made by different deposition methods having very large variations in growth environment energy. In the present work, we report a study of a-C:H films made by varying the growth energy in a continuous way, i.e., varying the plasma power, and/or pressure, and/or the substrate temperature during deposition. We have used ellipsometry, UV-visible absorption, and Auger electron spectroscopy (AES) profiling for sample characterization. These techniques give us energy gaps, density of state parameters, indexes of refraction, and sputtering rates. We have correlated these results with the growth environment energy in order to check the conjecture of Ref.(1). ExperimentalThe sample preparation will be discussed only very ...

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“…For example, Alterovitz et al (1983) investigated Si 3 N 4 thin films deposited by magnetic sputtering on GaAs substrates, and GaAs-AlGaAs multilayers using a variable angle spectroscopic ellipsometer. Merkel et al (1989) investigated GaAs/AlGaAs superlattices.…”

Section: Introductionmentioning

confidence: 99%

Optical Properties

Physics and Properties of Narrow Gap Semiconductors

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An enhanced sensitivity null ellipsometry technique for studying films on substrates: Application to silicon nitride on gallium arsenide

Cited by 21 publications

References 13 publications

Polar Polymeric Langmuir−Blodgett Films for Optical Applications

Polar Polymeric Langmuir−Blodgett Films for Optical Applications

Ellipsometric and Optical Study of Amorphous Hydrogenated Carbon Films

Optical Properties

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