Microwave Devices Microwave Passive Devices I 3 2008

Microwave Devices - Microwave Passive Devices I - 3 2008 / 1 학기 서광석 • S. N. U. EE Microwave Devices 2008

Attenuation (1) Attenuation R VVV UUU VVV G R – conductor loss c=R/2 Zo G – dielectric loss d=GZo/2 Total loss = c + d + r ( radiation loss ) 1. conductor loss top metal bottom metal x - edge에 많은 전류 flow Skin depth - skin depth Bottom side 전류가 dominant • S. N. U. EE (top metal) Microwave Devices 2008

Attenuation (2) • • Metal의 종류 ( Si IC ) : Al Cu (large ) ( RC time constant , delay ) (Ga. As MMIC) : Au, W/Au (high cost) (largest , 안정성) (thick) 2. dielectric loss ( ) E 1(air), E 2 (dielectric) 의 모양이 전체가 air인 경우와 같다고 가정할 때 [Ref. Collin pp. 153~155] * ceramic-loaded teflon : 30 GHz 이상에서 loss가 급격히 증가 (laser drilling for via) quartz for millimeter wave applications • S. N. U. EE Microwave Devices 2008

Attenuation (3) 3. radiative loss radiation Ref. ”Handbook of Microwave Integrated Circuits” by R. K. Hoffman conductor–backed dielectric waveguide leakage ( lowest mode : TMo with fc=0 ) - Pradiation f 2 - at f=fs : strong coupling for leakage ex) h=0. 5 mm, r=9. 6 h=0. 1 mm, Ga. As MMIC • S. N. U. EE fs = 60 GHz fs ~ 300 GHz Microwave Devices 2008

Microstrip Discontinuity (1) microstrip discontinuity Ref. 1. K. C Gupta 2. P. B Katehi et. al IEEE Trans. MTT p. 1029 E, H의 연속성을 만족시키기 위해 higher order mode , surface mode, radiation mode등이 excite. 1. open discontinuity Open end /4 circuit VVV (bias circuit) Vdc • S. N. U. EE Microwave Devices 2008

Microstrip Discontinuity (2) open radiation Coc VVV Coc r Goc radiation Coc Goc Coc Freq. <full-wave analysis> Coc • S. N. U. EE VVV UUU v Modified equivalent circuit C L R Coc , C, L, R = functions of w/h Ref : K. C. Gupta, et al. , “Microstrip Lines and Slotlines, ” Chap. 3, pp. 182 -183. Microwave Devices 2008

Microstrip Discontinuity (3) 2. gap • Coupler에 응용 • 작은 C 필요 시 응용 <simple model> 3. bend UUU current flow가 작은 영역 - capacitive compensated bend w r r>3 w • S. N. U. EE Chamfered bend d s Soptimum/d =0. 52+0. 65 exp(-1. 35 w/h) Microwave Devices 2008

Microstrip Discontinuity (4) 4. other discontinuities UUU step in width T junction improved T junction w UUU • S. N. U. EE 0. 7 w 0. 3 w 2 w or 2 h (longer) Microwave Devices 2008

Microwave Passive Elements – Resistor (1) Microwave Passive Elements ----- R , L , C, coplanar, transformer… Ref. “MMIC Design” chap. 3 1. Resistor - impedance matching Zo= 50 (precision) - bias resistor RG ~ 수백 RG (up to K ) Ø metal resistor (~50 : precision) Au t Au Ga. As W • R = Rㅁ*L/W = ( /t)* L/W precision을 위해서는 W , L density를 증가하기위해서는 , t L • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Resistor (2) • Ni. Cr : 60 ~ 600 -cm ex) Ni 0. 2 Cr 0. 8 , t= 900 Å : 180 -cm, Rㅁ=20 / (up to 40 / - industry standard) - (가열) electron beam evaporation • Ta. N : 280 -cm (좀 더 정확한 저항 값 구현) - nitrogen 분위기에서 Ta 증착 (reactive sputtering) Ø semiconductor resistor (bias resistor) I N -Ga. As Linear 영역에서만 사용 S. I. Ga. As V Rㅁ: 10 ~20% (부정확) ~500 /ㅁ • S. N. U. EE (large) • E < 3 k. V/cm 가 되도록 저항 길이 L을 결정 Microwave Devices 2008

Applications of Lumped Inductor ( I ) l Power Amplifier Application ( I ) Conventional Amplifier Bandwidth Enhanced Amplifier Shunt peaking Bandwidth ↑ ( Ref : S. S. Mohan, et al. , IEEE J. Solid- State Circuits, March 2000, p. 346~355) • S. N. U. EE Microwave Devices 2008

Applications of Lumped Inductor ( II ) l Power Amplifier Application ( II ) Bandwidth Enhanced Amplifier with shunt inductor L↑ L↑ ( Ref : S. S. Mohan, et al. , IEEE J. Solid- State Circuits, March 2000, p. 346~355) • S. N. U. EE Microwave Devices 2008

Applications of Lumped Inductor ( III ) l Voltage Controlled Oscillator (5 GHz) l Q of inductor ↑ l Phase Noise ↓ ( Ref : J. N. Burghartz, et al. , IEEE J. Solid- State Circuits, Dec. 1998, p. 2028~2034) • S. N. U. EE Microwave Devices 2008

Applications of Lumped Inductor ( IV ) l l Band Pass Filter (5. 4 GHz) Q of inductor ↑ l Q of BPF ↑, Insertion loss ↓ ( Ref : J. N. Burghartz, et al. , IEEE J. Solid- State Circuits, Dec. 1998, p. 2028~2034) • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Inductor (1) 2. Inductor Wire-bonding Air-bridge to prevent metal shortage < spiral inductor > Ø advanced inductor 구조 gap for small C - Ferrite core를 사용하면 L 증가 (수백 MHz 에서는 Ferrite core 성질 잃음. ) - microwave 응용으로 Ferrite가 없는 air-gap inductor 사용 C substrate * spiral 에 비해 high L, small C * MEMS process로 제작 가능 (yield, cost problem) • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Inductor (2) Ø inductance 계산 • Self-inductance (L, w: cm) w w s • Mutual-inductance 길이 L • w , s L - advanced processes t 6 m s w 10 m • w가 작으면 loss (t를 증가시켜 loss 감소 가능) • Industry standard : t=3 m , Au s/w=5 m /5 m, 10 m /10 m • S. N. U. EE 2. 5 m 2 m <MEMS process> <다층금속공정> - Si 공정 Microwave Devices 2008

Microwave Passive Elements – Inductor (3) Ø inductor for Si RF-IC spiral metal track Cground • conductive substrate로 인해 Csub Si substrate • typical substrate 20 -cm (conductive) Solutions (i) highly resistive substrate ~ 104 -cm availability , cost problem. (ii) inductor metal track 과 substrate 사이에 절연체 삽입 Csub • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Inductor (4) 절연체 Si. O 2 substrate r ~ 4 polyimide r ~ 3. 4 BCB (Csub 감소) Si substrate r ~ 2. 6 <다층 금속공정 응용> Ø inductor의 layout 효과 - Si RF IC에서는 inductor의 구현이 동작 주파수를 제한. large inductance (길이 길어짐) large fresonant & Q v 각 turn의 metal폭과 gap, core의 면적의 optimization에 의해 inductor의 Q값 최대화 – 실험 및 전자장 simulation • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Capacitor (1) 3. Capacitor <MIM capacitor> - 작은 series 저항 절연체 v Si DRAM에서 절연체 기술의 발전 : r 면적 줄임 (higher capacitance) Si. O 2 : r 4 Ta 2 O 5 : r =20~25 Hf. O 2, Zr. O 2 : r ~ 25 Al 2 O 3 : r =10 (현재) (Ba 0. 5 Sr 0. 5)Ti. O 3 : r > 300 (future) * Ta 2 O 5 : tan = 0. 02, unstable with bottom electrode * (Ba 0. 5 Sr 0. 5)Ti. O 3 - sputtering /annealing (550 C~800 C) 공정 사용 - 고온 열처리로 Ga. As에서는 사용 못함 (thermal damage) - unstable with bottom electrode : difficult to control stoichiometry • S. N. U. EE Microwave Devices 2008

Microwave Passive Elements – Capacitor (2) Ø MIM capacitor M 2 bottom metal Rt Lt UU VV M 1 C G UU VV VV UU • S. N. U. EE w 1 VV air bridge ( ( M 2 L 1 Cfringe Lb Rb M 1 Microwave Devices 2008

Microwave Passive Elements – Capacitor (3) v QMIM - bottom metal에 의해 결정 • Bottom metal - smooth surface를 위해 evaporation (0. 5 ~ 0. 8 m Au) • Top metal QMIM ~100 - electroplating (~3 m Au) (3 p. F capacitor) 1/QMIM = 1/Qconductor + 1/Qdielectric CMIM ~50 QMIM , fresonant CMIM 최대값 – 동작 주파수와 chip size에 의해 ~10 GHz CMIM 제한, 20 p. F 이하 (MMIC) f • • CMIM Csub substrate GND • S. N. U. EE • Csub § Csub 에 의해 signal loss 발생 fresonant Microwave Devices 2008

Microwave Passive Elements – Capacitor (4) v MIM capacitor layout -- metal 폭의 변화에 의한 discontinuity 효과를 감소시켜주는 layout (정사각형 직사각형) ( ( ( M 2 M 1 Ø Interdigital capacitor (0. 05~1 p. F) • Metal 두께 ~ 3 m • 동일 metal로 형성 • Precision capacitance • Unit area capacitance ~0. 3% of unit area capacitance of MIM • S. N. U. EE Microwave Devices 2008

Substrate Integrated Waveguide ( I ) ( Ref : D. Deslandes and K. Wu, IEEE Trans. MTT, Feb. 2003, p. 593 -596) • S. N. U. EE Microwave Devices 2008

Substrate Integrated Waveguide ( II ) ( Ref : B. Liu, et al. , IEEE MWCL, Jan. 2007, p. 22 -24) • S. N. U. EE Microwave Devices 2008