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DC Temperature Behavior of Hicum Arasch Lagies (IFX), Jörg Berkner (IFX), Ramana M. Malladi (IBM), Kim M. Newton (IBM), Scott M. Parker (IBM) June 15/16, 2004, Bordeaux, France • Temperature Dependent Modeling Problems • Reason for the Modeling Problems • Solution for the Modeling Problems • Results Secure Mobile Solutions N e v e r s t o p t h i n k i n g .

DC Measurement Results and Behavior at T=-40°C, 25°C and 125°C • Sketch of the Measurement Setup:Common-Emitter + c Vce T↓ - b e Ib Ib [uA] = 1, 2, 5, 8, 10, 15, 20 Vce = 0V to 3V T↓ • Results: • Slope of saturation region rises with decreasing T. • Active region current rises with decreasing T. Measurements at T=-40°C (blue), 25°C (black), 125°C(red)

DC Simulation Results with Hicum in Spectre at T=-40°C, 25°C and 125°C • Sketch of the Simulation Setup:Common-Emitter + c Vce - b e Ib Ib [uA] = 1, 2, 5, 8, 10, 15, 20 Vce = 0V to 3V • Results: • The saturation region is shifted to higher VCE for T < 0°C . • The active region current rises with decreasing T. Simulations at T=-40°C (blue), 25°C (black), 125°C(red)

Reverse Gummel Measurements at T=-40°C, 25°C and 125°C • In reverse Gummel IS cannot be fitted for all temperatures. • Measurements show: Ic, Ie, Ib and Is are all T-dependent. • This is true for reverse Gummel and in forward active mode. • How can the Is temperature dependence be fitted? T↑ Measurements at T=-40°C (blue), 25°C (black), 125°C(red)

Reason for Fitting Difficulties • The saturation current of the parasitic pnp substrate transistor ITSS is temperature-independent modeled. • If ITSS is fitted for T=25°C the current through the pnp substrate transistor becomes too big for T < 0°C, compared to the base current of the npn transistor. • This leads to • The shift for the DC output curves for T< 0°C toward higher VCE. • Bad fitting of IS in the reverse Gummel and in forward active mode over temperature. • Bad convergence behavior for T< 0°C.

Solution for the Fitting Difficulties (1) • For good results ITSS shows an exponential behavior with the temperature. • By using a similar function as used for the saturation current of the parasitic pnp transistor, ISP(T) in Vbic, this problem can be solved. • Here is

Solution for the Fitting Difficulties (2) • The exponential function for ITSS(T) leads to optimal agreement with measurements (ITSS’ = ITSS/area): Fitted ITSS’ values from measurements compared to the ITSS’(T) function

Solution for the Fitting Difficulties (3) • Some possibilities for the introduction of ITSS(T): • If a scaling file is available ITSS(T) can be implemented there (work around). • Generally ITSS(T) should be implemented in the model code.

Measurement vs. DC Simulation Results with Hicum in Spectre at T=-40°C, 25°C and 125°C using ITSS = ITSS(T) • With ITSS=ITSS(T) there is no shift of the saturation region to higher VCE. Meas. (dash-dotted) vs. sim. (solid) at T=-40°C. Meas. (dash-dotted) vs. sim. (solid) at T=25°C. Meas. (dash-dotted) vs. sim. (solid) at T=125°C.

Measurement vs. Reverse Gummel Results with Hicum in Spectre at T=-40°C, 25°C and 125°C using ITSS = ITSS(T) • With ITSS=ITSS(T) the low current region of IS in the reverse Gummel plot can be fitted accurately. Meas. (dash-dotted) vs. sim. (solid) at T=25°C. Meas. (dash-dotted) vs. sim. (solid) at T=125°C. Meas. (dash-dotted) vs. sim. (solid) at T=-40°C.

Conclusions • The temperature independence of ITSS for the parasitic pnp substrate transistor leads for some temperatures to a strong current imbalance compared to the base current of the npn main transistor. • This imbalance leads to • a shift of the saturation region in the DC output curves for T < 0°C, • a bad fitting of IS in the reverse Gummel and in forward active mode over T and • difficulties in the simulator convergence for some T. • The problem can be solved by using a T-dependent function for ITSS similar to the saturation current ISP(T), as used in Vbic. • ITSS(T) can be implemented in a scaling file or better in the model code itself.

Extra Foil (1)Reverse Gummel Measurement and Simulation with Hicum in Spectre at T=-40°C, 25°C and 125°C • In reverse Gummel IS cannot be fitted for all temperatures. Measurements at T=-40°C (blue), 25°C (black), 125°C(red) Simulations at T=-40°C (blue), 25°C (black), 125°C(red)

Extra Foil (2)IS Reverse Gummel Measurement and Simulation with Hicum in Spectre • Measurement and simulation in a technology of Infineon. • In reverse Gummel IS cannot be fitted for all temperatures. • Here the fitting was done for T=25°C (green). • For T=125°C (blue) the simulation deviates significantly. • For T=-25°C (red) no simulator convergence was achieved. Measurement solid lines, simulation dashed lines. For T = -25°C (red), 25°C (green), 125°C (blue)

+ c Vce - b e Ib Ib [uA] = 1, 2, 5, 8, 10, 15 Vce = 0V to 3V Extra Foil (3)DC Output Characteristics Simulation with Hicum in ADS • Here the same parameter set was used as in Spectre. • The default parameter set gives similar results. • For T < 0°C a shift of the saturation region to higher Vce can be observed. Simulation plot of ADS. For T = -40°C (blue), 25°C (black), 125°C (red).

Extra Foil (4)DC Output Characteristics Simulation with Hicum in ADSTemperature Sweep • Here the same parameter set was used as in Spectre. Simulation plot of ADS with Ib=10 mA. Temperature sweep with T = -40°C to 20°C in steps of 10°C.

Extra Foil (5)Forward Gummel Characteristic Hicum Simulation with ITSS=const., ITSS=ITSS(T), compared with measurements • In forward Gummel the change from ITSS=const. to ITSS=ITSS(T) leads to slight changes at T<0°C for higher VBE. • This comes closer to the measured values. Simulations and Measurements at T = -40°C (blue), 25°C (black), 125°C (red). Forward Gummel results with ITSS=const. (solid-symbol) and ITSS=ITSS(T). Included measurements (dash-dotted lines).

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