industry GaAs microelectronics
The biggest challenge that we have faced when developing our latest H2W technology is forming uniform 0.5 µm single and multiple gates for pHEMT devices around the HBT
mesa.That’s because the HBT mesa has a height of over 1.5 µ
m.After fine-tuning gate photoresist thickness and the lithography process, the success that we have had in addressing this challenge is seen in the quality of a 0.5 µm full-periphery gate
produced by us can also feature MIM capacitors with a capacitance of 570 pF/mm2
, stacked MIM capacitors with a capacitance of 870 pF/mm2 , thin-
film resistors with sheet resistance of 50 Ohm/ and an epitaxial mesa resistor with sheet resistance 175 Ohm/.
We define the dimensions of our 0.5 µm gate with an i-line stepper and use a single layer photo resist. A single recess, followed by metal evaporation, forms the gate.
Figure
3.Scanning electron microscopy photos for new generation H2W show that pHEMT with 0.5 µm full-periphery gate can be realized near the HBT transistors with high topology
The biggest challenge that we have faced when developing our latest H2W technology is forming uniform 0.5 µm single and multiple gates for pHEMT devices around the HBT mesa. That’s because the HBT mesa has a height of over 1.5 µm. After fine- tuning gate photoresist thickness and the lithography process, the success that we have had in addressing this challenge is seen in the quality of a 0.5 µm full-periphery gate realized near the HBT transistors with high topology – there is no reduction in quality compared to our stand-alone pHEMT technology (see figure 3).
Device characteristics HBTs produced with our PH50-20 process have a great set of characteristics. For example, the typical turn-on voltage is 1.265 V and DC current gain is 130 (see table 1 for more details). The cut-off frequency of this transistor is well above 30 GHz, so it can be widely used for constructing power amplifiers for Wireless LAN, UMTS and LTE standards.
The performance of the pHEMT is just as impressive as that of the HBT. Device characteristics of a 0.5 µm D-mode pHEMT produced with the PH50-20 process include a pinch-off voltage of -1V (Ids
=
Figure
4.pHEMTs produced by the new H2W process produce superior characteristics to those fabricated with the earlier H2W process. Comparisons of: (a) transfer curves,(b) I-V curves,(c) channel leakage currents,and (d) gate leakage currents
50
www.compoundsemiconductor.net October 2012
1mA/mm) and on-resistance of 1
Ohm.mm (see table 1 for details). Compared to the previous H2W technology, the latest version produces pHEMTs with a higher channel mobility, lower on-resistance, and a similar gate-drain breakdown voltage of about 18 V. The lower on-resistance stems from the move
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