D.K. Ghodgaonkar

Bio: D.K. Ghodgaonkar is an academic researcher. The author has contributed to research in topics: Dielectric & Relative permittivity. The author has an hindex of 2, co-authored 2 publications receiving 10 citations.

Microwave non-destructive testing of semiconductor wafers in the frequency range 8-12.5 GHz

Abstract: Microwave non-destructive testing (MNDT) using free-space microwave measurement (FSMM) system involve measurement of reflection (S/sub 11/) and transmission (S/sub 21/) coefficients in free-space. The measurement system consists of a pair of spot-focusing horn lens antenna, mode transitions, coaxial cables and a vector network analyzer (VNA). The inaccuracies in free-space measurements are due to two main sources of errors. 1) Diffraction effects at the edges of the material specimen. 2) Multiple reflection between horn lens antennas and mode transitions via the surface of the sample. The spot-focusing antennas are used for minimizing diffraction effects and free-space LRL (line, reflect, line) calibration method implemented on VNA eliminates errors due to multiple reflections. The time domain gating or smoothing feature of VNA is used to reduce post calibration errors in reflection and transmission measurements. In this paper, complex reflection coefficients were measured using FSMM system for silicon wafers backed by a metal plate. It was observed that the dielectric constants of the silicon wafers are higher than the values reported for intrinsic silicon wafers which maybe due to the presence of highly conductive epitaxial layer doped on the wafers. Results are reported in the frequency range of 8.0-12.5 GHz.

Accuracy considerations for dielectric measurements of semiconductor wafers using free space microwave measurement system in 8-13 GHz range

Abstract: An algorithm using only transmission measurements to calculate the complex permittivity of p-type and n-type silicon semiconductor wafers using a spot-focused free-space measurement system was developed The dielectric constant obtained was close to published values for silicon wafers The errors associated with the measurement of the complex permittivity values are discussed, and comparisons between the measured and calculated magnitude and phase of the forward reflection and transmission coefficients are presented In this method, the free-space reflection and transmission coefficients, S/sub 11/ and S/sub 21/, are measured for a silicon wafer sandwiched between two teflon plates which are quarter-wavelength at midband The actual reflection and transmission coefficient, S/sub 11/ and S/sub 21/ of the silicon wafers are then calculated from the measured S/sub 11/ and S/sub 21/ by using ABCD matrix transformation in which the complex permittivity and thickness of the teflon plates are known Results are reported in the frequency range of 8-125 GHz

A Free-Space Method for Complex Permittivity Measurement of Bulk and Thin Film Dielectrics at Microwave Frequencies

Abstract: A free-space, non-destructive method for measuring the complex permittivity of a double-layer bulk dielectrics and thin fllm oxide layers at microwave frequencies have been developed. The method utilizes a spot-focusing antenna system in conjunction with a vector network analyzer in the range of 18{26GHz. The bulk dielectric was measured using the Transmission Method and Metal-Backed Method, while the Metal-Backed Method was used to investigate the thin fllms. Both types of samples were sandwiched between two quarter-wavelength Te∞on plates to improve the mismatch at the frequencies of measurement. The thin fllm sample arrangement was backed by an additional metal plate. The double-layer bulk dielectric samples were Te∞on-PVC and Plexiglas-PVC, while the thin fllm samples consisted of SiO2 layers of difierent thicknesses grown on doped and undoped Si wafer substrates. The relative permittivity obtained for PVC ranged between 2.62 to 2.93, while those for Plexiglas exhibited values between 2.45 to 2.63. The relative permittivity of SiO2 deposited on these wafers was between 3.5 to 4.5. All these values are in good agreement with published data. The advantage of the method is its ability to measure the dielectric properties of the fllms at the mid- frequency band irrespective of the substrate type used. Simulations of the measurement setup were carried out using CST Microwave Studio and the simulation results agreed closely with the measurements.

Single layer coconut shell-based microwave absorbers

Abstract: This paper presents a study of single layer radar absorbing material made using coconut shell-based activated carbon. Flaxane-80 was used as binder and was mixed to give 10 wt%, 15 wt%, 20 wt% and 25 wt% variation of activated carbon obtained from coconut shell to study the microwave properties of the absorber material. An industry standard electromagnetic simulator was used to predict the absorber behaviour, while microwave non-destructive testing (MNDT) technique was used to measure microwave properties and reflection characteristics of the samples. The relative permittivity of 25 wt% carbon sample was found to be the highest with a value of 12. The sample also has the highest tan δ of 0.4. The thicknesses of absorbers made of 25 wt% carbon were varied at 3.2 mm, 6.4 mm, 9.6 mm and 13.8 mm to determine the reflection characteristics. The 6.4 mm sample was found to offer minimum reflection at 9.6 GHz with −22 dB reflection loss. Sample 9.6 mm has a minimum reflection loss of −17dB at 11.3 GHz. The results of this study offer great opportunities for RF application seeking for low cost and light-weight radar absorber material using coconut-shell.

Microwave non-destructing testing of rubber at X-band

Abstract: In this paper, the measurement of complex dielectric constant of natural rubber at microwave frequencies is reported. A free space, non-destructive technique was used to measure the parameter for several rubber samples at X band. The samples were prepared using different amounts of carbon filler to alter the dielectric properties so that the relation between filler content and er can be investigated. Our studies show that er and tan δ increase with the filler content. In addition, er showed a decreasing trend, while tan δ increased with frequency.

A free-space method for measurement of complex permittivity of double-layer dielectric materials at microwave frequencies

Abstract: Two methods for the calculation of complex permittivity of double-layer dielectric materials measured by a spot-focusing free-space measurement system have been developed. Standard materials have been used to test these methods and further works will be carried out on SiO 2 wafer. The dielectric constants obtained were close to the published values. The two methods developed are Transmission Method and Metal-Backed Method. The S 11 , S 21 , and S 22 are measured for Transmission Method, while only S 11 is measured for Metal-Backed Method. In both methods, the samples are sandwiched between two Teflon plates which are quarter wavelength at mid-band frequency. Results are reported in the frequency range of 18–26GHz.

Binomial multi-layer coconut shell-based rubber microwave absorber design

Abstract: This paper presents results of a study on multi-layer binomial radar absorbers constructed from rubber latex using coconut shells as fillers The microwave properties of the absorbers were measured using a microwave non-destructive testing (MNDT) technique The performance of single layer, two-layer and three-layer absorbers were simulated using a commercial 3D electromagnetic simulator Single layer and two-layer absorbers have bandwidths of 11% and 8% respectively, while the three-layer absorber exhibited the widest bandwidth of 85% The effect of carbon content and the absorber thickness has been studied and show that increasing absorber thickness and carbon content in the samples shifted the reflection frequency while the bandwidth remained