Alan N. Downey

Characterization of thin film microstrip lines on polyimide

This paper presents an in depth characterization of thin film microstrip (TFMS) lines fabricated on Dupont PI-2611 polyimide. Measured attenuation and effective dielectric constant is presented for TFMS lines with thicknesses from 2.45-7.4 /spl mu/m and line widths from 5-34.4 /spl mu/m over the frequency range of 1-110 GHz. The attenuation is separated into conductor and dielectric losses to determine the loss tangent of Dupont PI-2611 polyimide over the microwave frequency range. In addition, the measured characteristics are compared to closed form equations for /spl alpha/ and /spl epsiv//sub eff/ from the literature. Based on the comparisons, recommendations for the best closed form design equations for TFMS are made.

High frequency interconnects on silicon substrates

The measured propagation constant of coplanar waveguide (CPW) on silicon wafers as a function of the line dimensions and the resistivity of the Si wafer; CPW on GaAs wafers as a function of the line dimensions; and thin film microstrip (TFMS) fabricated with polyimide on the surface of a silicon wafer is presented. It is shown that the attenuation of CPW on 2500 /spl Omega/-cm Si wafers and of TFMS with a polyimide thickness of 4 /spl mu/m or greater is comparable to the attenuation of similar lines on GaAs.

High-temperature RF probe station for device characterization through 500/spl deg/C and 50 GHz

A high-temperature measurement system capable of performing on-wafer microwave testing of semiconductor devices has been developed. This high-temperature probe station can characterize active and passive devices and circuits at temperatures ranging from room temperature to above 500/spl deg/C. The heating system uses a ceramic heater mounted on an insulating block of NASA Shuttle tile. The temperature is adjusted by a graphical computer interface and is controlled by the software-based feedback loop. The system is used with a vector network analyzer to measure scattering parameters over a frequency range from 1 to 50 GHz. The microwave probes, cables, and inspection microscope are all shielded to protect from heat damage. The high-temperature probe station has been successfully used to characterize gold transmission lines on silicon carbide at temperatures up to 540/spl deg/C.

Low-temperature microwave characteristics of pseudomorphic In/sub x/Ga/sub 1-x/As/In/sub 0.52/Al/sub 0.48/As modulation-doped field-effect transistors

Low-temperature microwave measurements of both lattice-matched and pseudomorphic In/sub x/Ga/sub 1-x/As/In/sub 0.48/As (x=0.53, 0.60, and 0.70) channel MODFETs on InP substrates were carried out in a cryogenic measurement system. The measurements were done in the temperature range of 77 to 300 K and in the frequency range of 0.5 to 11.0 GHz at different bias conditions. The cutoff frequency (f/sub T/) for the In/sub x/Ga/sub 1-x/As/In/sub 0.52/Al/sub 0.48/As MODFETs improved from 22 to 29 GHz, 29 to 38 GHz, and 39 to 51 GHz, for x=0.53, 0.60, and 0.70, respectively, as the temperature was lowered from 300 to 77 K, which is approximately a 31% increase at each composition. No degradations were observed in device performance. These results indicate an excellent potential of the pseudomorphic devices at low temperatures.<<ETX>>

High-temperature probe station for use in microwave device characterization through 500°C

A high-temperature measurement system capable of performing on-wafer microwave testing of semiconductor devices has been developed. This high temperature probe station can characterize active and passive devices and circuits at temperatures ranging from room temperature to above 5OO°C. The heating system uses a ceramic heater mounted on an insulating block of NASA shuttle tile material. The temperature is adjusted by a simple graphical computer interface and is automatically controlled by the sohare-based feedback loop. The system is used with a Hewlett-Packard 8510C Network Analyzer to measure scattering parameters over a frequency range of 1 to 50 GHz. The microwave probes, cables, and inspection microscope are all shielded to protect from heat damage. The high temperature probe station has been successfully used to characterize gold transmission lines on silicon carbide at temperatures up to 540°C.

Measured propagation characteristics of coplanar waveguide on semi-insulating 4H-SiC through 800 K

Wireless sensors for high temperature industrial applications and jet engines require RF transmission lines and RF integrated circuits (RFICs) on wide bandgap semiconductors such as SiC. In this paper, the complex propagation constant of coplanar waveguide fabricated on semi-insulating 4H-SiC has been measured through 813 K. It is shown that the attenuation increases 3.4 dB/cm at 50 GHz as the SiC temperature is increased from 300 K to 813 K. Above 500 K, the major contribution to loss is the decrease in SiC resistivity. The effective permittivity of the same line increases by approximately 5% at microwave frequencies and 20% at 1 GHz.