Future devices for Information Technology 2003. 4. 4. Songcheol Hong
Contents Electronic Devices (processing devices) High speed devices(digital, analog, RF) High power devices Memory devices Optical Devices QWLD, QDLD Optical communication devices GaN based Devices Display
High speed devices Digital, Analog(RF) DSP upto Microwave frequencies IEEE MTT Vol. 50, N0. 3, 2002 p900
Trends in Transmitter Architecture(Mobile) High Speed DSP (7GHz) DC-DC converter Vector Modulator DSP SDR One Chip Radio Supply voltage control Bias control
Smart PA Heterodyne type Base/gate bias voltage control GaAs based PA Gate/base bias control
Dynamic supply voltage (DSV) PA Direct conversion Supply Voltage Control Dynamic Supply Control DSP clock speed ~ 10MHz GaAs PA + CMOS DC-DC converter SiGe BiCMOS
Digital Predistorer Digital predistorter SiGe BiCMOS PA or CMOS switching PA
Direct RF synthesis Direct RF Synthesis DSP clock speed ~ 7 GHz CMOS Switching PA and controller
High speed Power Devices • MESFET/ HEMT High Efficiency / high Linearity Temperature stability Negative bias Develop Enhancement FET • MOSFET/LDMOS Low Efficiency Temperature Stability Single bias
HBT High Efficiency / High Linearity Single bias High power density Bad temperature stability introduce Ballast R, careful bias circuit
Fig. 1. A cross-section of IBM's SiGe HBT structure, which was used to obtain a record-breaking ft value of 350 GHz. Credit: IBM.
Power transistor (FETs) Circuit design : Power combine : Unit transistor
HBT with Ballast R ( Via hole and Air bridge) 12 finger Rb=50 8 finger Rb=50
Power Cell 64 finger
MOS power cell Conventional 구조 • Conventional 구조 • Poly gate와 drain metal의 저항이 클것으로 예상 • Source metal이 drain metal을 덮는 구조이므로 Cds가 클것으로 예상
FET vs. HBT (size) HBT’s (being vertical in structure) consume less die area than an equivalent FET based production technology Example> take a PA line-up for GSM (Pout=35dBm, Vbat=3.2V)
Ballasting • HBT devices must be BALLASTED to ensure thermal stability • Thermal run-away is avoided if a sufficiently large ballast resistance is placed in either the emitter or the base of the HBT • In a multi-finger array, one device may be hotter than other. The hotter device will experience a drop in Vbe (-2mV/oC) which will cause it to draw even more current from a fixed-base-voltage supply… thus it will get even hotter. The end result is finger burn-out
Ballasting (conti…) • Three methods are available to ballast your circuit
HBT bias circuit • Diode-bias and current-mirror circuits can be seen here: • • The key differences are: • - Diode bias requires the diode to draw current, which can be significant • Current mirror does not track as well over temperature • Current mirror has the “2 Vbe” reference-voltage issue
CMOS and LDMOS power TR IEEE EDL, Vol. 21, No.2, p81, YueTan et al.
Conclusions I High speed digital and analog devices • Submicron CMOS(0.18um) is • covering upto 10Gbps and 10GHz range. • Submicron CMOS(0.05um) will be • covering upto 40 Gbps and 40 Ghz range. • Digital part will dominate Analog and RF • Finally, only power amp in RF with digital control • will survive • 5. LDMOS+CMOS will be a winner in Power applications • 6. SiGe may be used in high speed digital and • 10-60 GHz range RF. • 7. GaAs HBT is used in Power and Low noise application • 1- 40 GHz • 8. InP HBT and HEMT are used • in high frequencies(above 30Ghz)
DRAM Figure 7.4: Simplified DRAM schematic.
Figure 7.7: Vertical stacked capacitor: Top-SEM photograph of the storage plate. Bottom-Solid model and grid of the simulated structure (only the material POLY1 is displayed).
FRAM Figure 1. Schematic cross section of a FRAM unit cell [1T/1C]
Conclusion II Memory DRAM: Design rule becomes smaller, Ferroelectric Materials make C smaller, New Structures Nonvolatile Memory: Flash Nano-flash, QD flash FRAM MRAM
Figure 2. TEM micrograph showing the core of a 5-QWR Laser. The wires are positioned inside the 2D optical waveguide in an asymmetric configuration in order to maximize the overlap of the optical mode with Quantum wire grown on V groove
LD, LED ---Conclusion III Laser diode QW QD ---- High power LD VCSEL QW QD ---- Low threshold Current Blue light sources --- GaN Storage illumination
Standard & Applications Optical communication devices Expected 10 Gigabit Ethernet solution • Method to overcome limit • 42.5 Gb/s WWDM with installed MMF & SMF • 10 Gb/s TDM with SMF & 1300nm LD Ref.) Tutorials, Agilent, 2000 OE conference