Budapest University of Technology and Economics Department of Electron Devices Microelectronics, BSc course Bipolar IC technology: set of elements

Budapest University of Technology and Economics Department of Electron Devices The bipolar process ► Steps / masks Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Structure of bipolar IC transistors burried layer collector n type island p-Si substrate base contact emitter base collector contact Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 1. n+ burried layer doping (for collector regions) M p n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 2. n epi layer growth for the active islands n p n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 3. p type isolation doping (deep diffusion through the n epi layer) M n p p n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 4. p+ base diffusion M n p p p+ n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 5. n+ emitter diffusion (also for better collector contact) M n p p p+ n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps n p p p+ 6. contact window opening p+ n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 6. contact window opening M n p p p+ n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 7. metallization pattern n p p p+ n Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Major process steps 7. metallization pattern M n p p p+ n+ Masks needed for a bipolar process: burried layer (n+) isolation (deep p through n epi) base (p) emitter (n+) contact windows metallization pattern The process is optimized for creating good NPN transistors Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Set of components available in bipolar IC-s ► Resistor with base diffusion ► Resistor + emitter diffusion ► PNP transistors ► Thin film capacitance ► Layout of an OpAmp

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set available in bipolar IC processes

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Detail of a bipolar IC – as seen by a scanning electron microscope

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s npn (vertical) transistor Island (well) Substrate Buried layer Emitter Base

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s the isolation diffusion

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Structure of an npn IC transistor Island (well) Substrate Buried layer Emitter Base metal

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s npn transistors Effective emitter edge at the base contact side (I=2 A/cm), EB br.down: 5-6 V, CB br.down V, f T = MHz Process optimized for the npn (vertical) transistors

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s High current npn transistors

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Area efficient solutions: two transistors in a common isolation well, multi-emitter transistor Element set in bipolar IC-s Different npn transistors

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Different npn transistors Effective emitter edge at the base contact side (I=2 A/cm)

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Resistor with base diffusion island (well)

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Resistor with base diffusion There could be multiple resistors in the same isolation well The well must be connected to +U CC !

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Resistor with base diffusion, folded as a meander Accuracy, parasistics

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET How to make components VERY MUCH identical? same layout shape same position/orientation close to eachother larger than minimal size same temperature

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Resistor with base diffusion, cross section reduced by emitter diffusion

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s value: few times 100 k  emitter diffusion base diffusion Slightly nonlinear Limited voltage range Resistor with base diffusion, cross section reduced by emitter diffusion

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET small emitter diffusion resistor (connection underpass), value cca. 2  Emitter diffusion Metallization Element set in bipolar IC-s

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Lateral pnp transistor

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Multiple transistors in common well Element set in bipolar IC-s Lateral pnp transistor

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Forms a current mirror Element set in bipolar IC-s Lateral pnp "sector" transistors overlapping contact window

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET I I I 3I Also with circular shape! Element set in bipolar IC-s Lateral pnp "sector" transistors

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET n + no buried layer push and pull amplifier (B) Element set in bipolar IC-s Vertical pnp transistor vertical pnp structure

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET d ox : 0,1  m (50 V) C spec : 3-400pF/mm 2 Element set in bipolar IC-s The thin film capacitor Metal

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s Thin film (metal-SiO 2 -n + ) capacitor in an OpAmp Value: cca. 30pF C spec : 3-400pF/mm 2

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Compare the size of the capacitor and the transistors! Element set in bipolar IC-s Thin film (metal-SiO 2 -n + ) capacitor in an OpAmp

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Element set in bipolar IC-s The pn junction as a capacitor The space charge capacitance can be utilized, but voltage dependent (non-linear) may not be forward biased! EB: 1000pF/mm 2 (up to 5 V) CB: 150pF/mm 2 (up to ~50 V)

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET OpAmp layout, component arrangement T1, T2: NPN, input differential pair T3, T4: PNP, lateral T5, T6, T7: NPN T10, T11, T13: PNP lateral transistors D1, D2: diodes T16-17: NPN darlington T19-21: 3 NPN transistors in a common well R1, R6: large resistors R7: base+emitter diff. resistor R8, R9: small resistors T22: PNP vertical T23: NPN vertical (high current) Symmetry – to assure same thermal feedback path. This layout is not yet the best.

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Thermal effects in analog IC-s: a bipolar OpAmp ► Thermal impedances ► Thermal feedback in case of an OpAmp ► How does the layout influence the thermal feedback ► Layout – thermally optimized

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET The thermal impedances The transfer impedance Z th complex valued The self impedance T 1 temperature rise

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Thermal feedback – in an OpAmp Stationary state, V OUT > 0   -2 mV/ o C

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Thermal feedback – in an OpAmp Stationary state Effect on the open loop characteristic

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Thermal feedback – in an OpAmp Methods for analysis Both measurements and simulations were done. A well known, commercially available circuit was studied (  A741 OpAmp). Both stationary state and dynamic behaviour. Identical type from different IC venors: different layout designs realizing the same electrical schematic. Actual layout (component arrangement) was identified by "reverse engineering".

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Details of the model Schematic of the OpAmp Physical layer structure Device under test:  A741 OpAmp Yellow transistors considered by electro-thermal model

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Reverse engineered layouts Layout "A"

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Reverse engineered layouts Layout "B"

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Open loop characteristics (measurement and simulation) Layout "A"

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Layout "B" Open loop characteristics (measurement and simulation)

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Thermal effects in the output impedance Frequency domain analysis

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET Layout "A", upper transistor on, G=10 4 Effect appears even if there is no load! Frequency domain analysis

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET "A" "B" Difference only in layout! Frequency domain analysis

Budapest University of Technology and Economics Department of Electron Devices Microelectronics BSc course, Element set in bipolar IC-s © András Poppe & Vladimír Székely, BME-EET "A" "B" Input differential pair (common centroid) Output transistors The ideal layout