Following are pictures of our own pHEMT. Black-and-white photographs are taken by using SEM and color ones are taken by using a camera attached to an optical microscope.
T-gate process
T-gate e-beam lithography
MESA etch
Selective channel etch
4 finger AlGaAs/InGaAs pHEMT
8 finger AlGaAs/InGaAs pHEMTT
Following are SEM photographies of top view of our fabricated HBTs before metal2 process.
Emiter size of 2 x 20 conventional HBT
0.4 x 2 submicron HBT
0.4 x 1.5 submicron HBT
2 x 20 power HBT
0.6 x 10 power HBT
Following is taken by using SEM. It is a picture of our own sub-micron MSM photodetector which has already characterized.
Submicron MSM Photodetector
Connectible with HEMT Fabrication, can be made a one chip for optic receiver.
P-I-N Photodetector
Active area diameter : 60 mmFollowing are pictures of our own passive device elements for MMIC and some process results, such as though via hole, plating and airbridge process.
NiCr Thin Film Resistor (TFR)
Metal Insulator Metal (MIM) Capacitor
Square Spiral Inductor
Circular Spiral Inductor
Lange Coupler 90-degree 3-dB Coupler, 40.5~42.5 GHz
Wilkinson Power Divider
Rat-race Coupler
180-degree 3-dB Coupler, 40.5~42.5 GHz
Several MSTL and GCPW discontinuity patterns
Airbridges
Through Via Hole Process
Electroplating
We are completely equipped for device characterization such as device parameter extraction (HP IC-CAP), and low frequency noise measurement. And we will be soon equipped with high frequency(up to 40GHz) noise measurement system. We have been carrying out GaAs based power HBT modeling and p-HEMT modeling as well as noise parameter extraction. Following is a usual parameter extraction step.
Electroplating
Following are our several systems for device characterization.
Epitaxial layer growth is one of the most important technologies for III-V semiconductor millimeter-wave transistors and optical devices. This technology offers the precise bandgap engineering which can improve the performance of the devices and extend their applications.MBE and CBE are sophisticated deposition techniques performed in ultra high vacuum primarily for the growth of III/V materials, and II/VI materials such as GaAs and InP.High speed electronic, optoelectronic and optical devices involve complex semiconductor heterostructure layers, and must be grown by advanced thin-film growth techniques such as Molecular Beam Epitaxy or Chemical Beam Epitaxy.Our lab. is operating MBE and CBE to deposite epi-layers for HEMT, HBT and Photodetectors.
In MBE, atoms are delivered to a substrate through an ultra-pure, ultra-high vacuum atmosphere. The atmosphere provided by the MBE chamber allows the atoms to arrive on the substrate without collision with other atoms or molecules, therefore keeping the growth from any contaminants. The heated substrate surface allows the arriving atoms to distribute themselves evenly across the surface forming an almost perfect crystal structure. In MBE, the substrate is placed in an UHV chamber with direct line of sight to several elemental species each of which is in an evaporation furnace commonly referred to as an effusion cell. Through use of shutters and precise control of the effusion cell temperatures almost any material composition and doping can be achieved. Further, the composition may be controlled with a resolution of virtually one atomic layer. A UHVchamber of MBE is following.
In MBE, atoms are delivered to a substrate through an ultra-pure, ultra-high vacuum atmosphere. The atmosphere provided by the MBE chamber allows the atoms to arrive on the substrate without collision with other atoms or molecules, therefore keeping the growth from any contaminants. The heated substrate surface allows the arriving atoms to distribute themselves evenly across the surface forming an almost perfect crystal structure. In MBE, the substrate is placed in an UHV chamber with direct line of sight to several elemental species each of which is in an evaporation furnace commonly referred to as an effusion cell. Through use of shutters and precise control of the effusion cell temperatures almost any material composition and doping can be achieved. Further, the composition may be controlled with a resolution of virtually one atomic layer. A UHVchamber of MBE is following.
The idea of CBE is to use precursors similar to those used in MOCVD and introduce them into an MBE chamber.When, actually, solid group III sources and gaseous group V sources are used, gas-source molecular beam epitaxy (GSMBE) is the correct name. The idea behind the change away from solid elemental sources is the simplicity of the control of the precursors. It is difficult to control effusion cells with solid material in order to keep the molecular flow constant. The amount of material in the cell diminishes gradually, changing the optimal temperature of the cell. The metalorganic sources have a constant vapor pressure, if the temperature is kept constant, until supply is exhausted. The adaptation of sources from MOCVD to CBE also makes accurate control of the growth easy. Another interesting aspect is the change to longer diffusion lengths for metal-organic precursors on a semiconductor surface. This makes it possible to get a better long-range uniformity in the grown layers. The greatest advantage of MBE over CBE today is the maturity of the former technique. It is more developed and the growth kinetics are better understood both because growth conditions have been studied extensively and because the task of describing elemental molecular reactions with a surface is less complex.
[refered to] GaAs High-Speed Devices Physics, Technology, and Circuit Applications C.Y. Chang, Francis Kai
Following are two epi-structures of our active devices; InGaP/InGaAs/GaAs pHEMT and InP/InGaP HBT.
