N.I. Cameron

A high performance, high yield, dry-etched, pseudomorphic HEMT for W-band use

A GaAs pseudomorphic HEMT process has been optimised for high performance and yield at W-band. Several key nano-fabrication techniques are explored for performance, manufacturability and process sensitivity. The molecular beam epitaxially grown pHEMT layer is optimised for reduced short channel effects, high transconductance (690 mS/mm) and reliability. Electron-beam lithography produces ultra short T-gates with high reproducibility. Selective reactive ion etching enables both the depth and width of the gate recess to be accurately controlled. 0.2 /spl mu/m pHEMTs with two 50 /spl mu/m gate fingers exhibit average values for f/sub T/ and f/sub max/ of 121 and 157 GHz with low standard deviations of 4.6 and 2.9 GHz respectively.<<ETX>>

The effect of CH 4 /H 2 RIE on thin highly doped GaAs layers

Abstract The effects of CH 4 /H 2 RIE on thin, highly Silicon doped, MBE grown GaAs layers have been assessed by Hall measurements of sheet carrier, concentration, N sh , and Hall mobility, μ H . Hydrogen passivation of the donor atoms caused a three orders of magnitude decrease in sheet concentration and consequent increase in mobility due to reduced ionised impurity scattering. The electrical activity of the material was recovered, by performing a short anneal at 400°C, to a level dependent on RIE induced damage which is found to be minimised by etching at a reduced DC bias level of 80 V. Mobility was restored, by annealing, to values comparable with wet etched material. GaAs MESFET devices, with excellent DC and RF characteristics, have been fabricated using 0.1 μm gates recessed by CH 4 /H 2 RIE.

94 and 150 GHz coplanar waveguide MMIC amplifiers realized using InP technology

We report the design, fabrication and measurement of a three stage W-band amplifier with up to 22 dB gain at 94 GHz and a single stage D-band amplifier with 5 dB gain at 150 GHz. Circuits were designed and fabricated in coplanar waveguide technology using a 0.121 /spl mu/m T-gate lattice matched InP HEMT technology.

Fabrication and high frequency characterisation of GaAs MESFETs with gate lengths down to 30 nm

Abstract This paper describes a process to fabricate GaAs MESFETs with gate lengths in the range 270 to 30nm suitable for high frequency characterisation. Electron beam lithography was used to define all device levels on layers grown by molecular beam epitaxy (MBE). Processing included a dry etched mesa for isolation, low temperature annealed ohmic contacts, and a gate recess etch containing a wetting agent to improve etching uniformity. The MESFETs were characterised at DC and high frequency. 30nm gate length devices exhibited DC transconductances of up to 710mS/mm and unity gain cut off frequencies of up to 150GHz extrapolated at 6dB/octave from 20GHz.

150GHz Coplanar Waveguide MMIC Amplifier

We report the design, fabrication and measurement of a single stage D-Band amplifier with 3-4dB gain at 150GHz. In addition a three stage D-Band amplifier with 7.5dB gain at 153GHz is reported. Circuits were designed and fabricated in coplanar Waveguide technology using a 0.12¿m T-gate lattice matched InP HEMT technology.

Basic of Pseudomorphic Hemts Technology and Numerical Simulation

This chapter consist of two parts. In the first part we describe the technology used in the Nanoelectronics Research Centre of Glasgow University for fabrication of high performance 200 - 100 nm gate length Pseudomorphic HEMTs (PsHEMTs). Most of the fabrication sequence is fairly standard and gives a good overall impression of the basic technological steps involved in the fabrication of modern PsHEMTs. There are however some specific solutions which distinguish our PsHEMT technology from the recipes adopted by other university and industry based groups. Among those ’secrets’ are the use of an As2 source with a low temperature AS4 cracker in the MBE growth of the vertical layer structure, and a new selective and low damage recess reactive ion dry etching process based on SiCl4/SiF4 chemistry.

Fabrication and Simulation of 0.1 μm Pseudomorphic HEMTs

When the gate length of the pseudomorphic HEMTs (PsHEMTs) approaches 0.1 μm, short channel effects become limiting factor for the device performance, leading to a large negative threshold voltage shift, increase in the output conductance, degradation and subthreshold slope reduction. Most of the authors attribute the short-channel effects in HEMTs mainly to the de-confinement of the channel carriers [1]. The proposed solution is enhancement of the confining step potential below die channel together with a reduction of the distance between the gate and the channel in order to preserve a large aspect ratio.