A 1mm2 flip-chip SP3T switch and low noise amplifier RFIC FEM for 802.11b/g applications Cody Hale Bob Baeten Wireless Connectivity Business Unit Outline • Introduction • Process Technology • Cu Pillar Overview • Design Considerations • Measured Results • Summary Wireless Connectivity Business Unit Introduction • Motivation • Customer demand is driving mobile handsets to be smaller while adding functionality, specifically WLAN radios • This requires the radio front ends to be much smaller in footprint area but still perform well • Challenge • To design a WLAN front end module with 25% of the footprint area than an existing RFMD product (RF5501) while maintaining the same performance Wireless Connectivity Business Unit Size Comparison RF5501, 2x2 mm RF5511, 1x1 mm Wireless Connectivity Business Unit Process Technology • RFMD’s 0.5um E/D mode GaAs pHEMT • 3 Metal Interconnects, Top metal is 2um thick • MIM Capacitors, 138 and 755 pF/mm2 • Resistors, Thin film = 100 Ω/□ and Epi = 87 Ω/□ • E/D pHEMT with highly linear D-mode FET switches and low noise E-mode FET amplifiers combined on die • Flip chip substrates thinned to 300um Wireless Connectivity Business Unit Cu Pillar Overview Cross Section of RF5511 • Cu Pillars with an Sn Solder cap can be run on the same assembly flow as Solder bumps, making integration into an existing flip chip assembly line easy. Wireless Connectivity Business Unit Block Diagram of RF5511 Switch Controls E-mode LNA with Bypass D-mode SP3T Wireless Connectivity Business Unit Die Photograph 0.990mm 0.984mm Minimum Bump Pitch 0.190mm Wireless Connectivity Business Unit Application Schematic Wireless Connectivity Business Unit S-Parameter Test Setup For S-Parameters, the RF5511 was assembled to an FR-4 4-layer Evaluation Board and connected to an Agilent 5071C VNA, -20dBm input power and measurements were de-embedded to the Cu Pillar landing pads on the FR-4 board. Wireless Connectivity Business Unit Noise Figure Test Setup For Noise Figure, the RF5511 was assembled to an FR-4 4-layer Evaluation Board and connected to an Agilent 8974A with a 6dB ENR N400A noise source and measurements were de-embedded to the Cu Pillar landing pads on the FR-4 board. Wireless Connectivity Business Unit Measured Results, LNA RF5511Typical Noise Figure RF5511 Typical S-Parameters 15 2.8 2.6 10 2.4 5 2.2 NF (dB) Gain, S11, S22 (dB) 3 Gain Input RL Output RL 20 0 25C NF -30C NF 85C NF 2 1.8 -5 1.6 -10 1.4 1.2 -15 1 -20 2300 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 Freq (GHz) 2400 2450 Freq (GHz) 2500 Wireless Connectivity Business Unit Measured Results, TX Switch 0 -10 -1 -13 -2 -16 -3 -19 -4 -22 -5 -25 -6 -28 -7 -31 -8 -34 -9 -37 -10 -40 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 Frequency (GHz) Return Loss, Isolation (dB) Insertion Loss (dB) RF5511 Switch S-Parameters TX Insertion Gain ANT Return Loss TX Return Loss Isolation Wireless Connectivity Business Unit Measured Results, Wire-bond Comparison RF5511 vs. RF5501 NF RF5511 vs. RF5501 Gain 20 4 18 3.5 16 3 12 5511 Gain 10 5501 Gain 8 6 NF (dB) Gain (dB) 14 2.5 RF5511 NF RF5501 NF 2 1.5 1 4 0.5 2 0 2.3 2.4 2.5 Freq (GHz) 2.6 0 2380 2400 2420 2440 2460 Freq (MHz) 2480 2500 2520 Wireless Connectivity Business Unit Switching Speed, BT Off to BT On Legend CH1: CRX & LNA_EN CH3: CBT CH4: BT RF Port 77 ns to turn BT switch branch on. TX switching time is the same Wireless Connectivity Business Unit Switching Speed, RX OFF to RX ON Legend CH1: CRX & LNA_EN CH3: CBT CH4: RX RF Port 142 ns to turn RX switch branch and LNA on Wireless Connectivity Business Unit Competitive Comparison RFMD RF5511 M/A-Com MAMF009448-000DIE SiGe SE2600S Size (mm) 0.984x0.990x0.38 1.095x0.925x0.33 1.07x1.05x0.38 Bump Technology Cu Pillar SnAg Solder Bump SnAg Solder Bump Switch IL (dB) 0.5 0.65 0.5 LNA Gain (dB) 11 12 12 LNA NF (dB) 1.9 1.9 1.8 # SMD's Required 5 6 Unknown Wireless Connectivity Business Unit Summary • Cu pillar bumping shows to be a viable solution for decreasing area consumption in front end modules. • Performance of the RF5511 with Cu Pillars is slightly better than it’s QFN-based cousin, RF5501, and only occupies 25% of the area. • RFMD’s RF5511 die is even smaller than competitive FEM’s published with datasheets with room to shrink another 25-30% • We believe GaAs flip-chip front end module solutions will soon be have a much larger presence in handset radios due to the area and weight savings made possible, and RFMD has chosen Cu Pillar as it’s preferred bump technology.