Standard Bipolar Process Research Articles

A 3.2 ppm/°C curvature-compensated bandgap reference with wide supply voltage range

A novel bandgap reference (BGR) with low temperature and supply sensitivities, which is compatible with standard Bipolar and BiCMOS processes, is presented in this paper. Utilizing exponential curvature compensation (ECC) and translinear loop circuit (TLC), high-order curvature compensation is realized to reduce temperature drift. Besides, two feedback loops are embedded in the circuit to enhance the stability and to reduce the dependence on supply voltage. Experimental results of the proposed BGR implemented with 1-μm Bipolar process demonstrate that a temperature coefficient (TC) of 3.2ppm/°C is realized, a power supply rejection ratio (PSRR) of 60dB is achieved without filtering capacitors, and the line regulation is better than 0.088mV/V from 3.5V to 30V supply voltage dissipating a maximum supply current of 39μA. The active area of the proposed BGR is 700μm×750μm.

HHNEC 0.18um BCD Technology for High Density Power Integration

A new 0.18um Bipolar CMOS DMOS (BCD) integrated platform is presented. This technology provides both N type and P type power LDMOS with capability of voltage up to 40V applications; these power LDMOS devices have competitive specific on-resistance; the parasitical miller capacitance and SOA of power LDMOS devices are optimized by careful device and layout design; it also provides HVCMOS with voltage up to 40V analog application; the bipolar devices in this technology are also optimized for power switching as standard bipolar process offers. The 1.8V/5.0V CMOS devices are performance compatible with industry main stream 1.8V/5.0V CMOS technology. This platform is modularized with various options; it can be separated into 1.8V/5.0V mixed 40V HVCMOS process, 5.0V Vgs 40V Vds 0.18um backend BCD process and 1.8V/5.0V Vgs 40V Vds 0.18um BCD process, which customers can easily choose for their product needs without any process tuning.

Three terminals optoelectronics devices integrated into a silicon on silicon waveguide

In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices.

A new sensor structure using the piezojunction effect in PNP lateral transistors

Due to the piezojunction effect, the I C( V BE) characteristics of bipolar transistors are affected by mechanical stress. It appears that this effect is the dominant source of inaccuracy of many analogue circuits, such as smart temperature sensors and band-gap references. On the other hand, advantage can be taken from this effect to realize new mechanical sensors. This paper shows how to minimize or to maximize the influence of the piezojunction effect of lateral PNP (L-PNP) transistors on [1 0 0] silicon wafer. The L-PNP transistors are available in any standard bipolar or CMOS process and are suited to realize low cost sensor implementation. As compared to sensors based on the piezoresistive effect, the new sensor offers the advantage that it is very small, has a reduced power consumption and can also provide a temperature measurement using the base–emitter voltage ( V BE). The current mirror gauge factor amounts to 176; the nonlinearity is less than ±1% and the temperature coefficient of the gauge factor (TCGF) is 1.75×10 −3°C −1.

Measurement of buried oxide thermal conductivity for accurate electrothermal simulation of SOI device

Finite element simulations demonstrate that the thermal conductivity of the buried oxide is an important parameter for the modeling of the thermal behavior of silicon-on insulator (SOI) devices. There is uncertainty about the conductivity of different forms of SiO/sub 2/, particularly that of buried oxides. This paper presents a novel approach to measure this conductivity, using structures that are compatible with standard bipolar or CMOS processes. Thermal conductivity values of 0.66 and 0.82 W/mK, respectively, were found for 300-nm BESOI and 420-nm SIMOX oxides at room temperature. The measured variations of thermal conducitivity with temperature agree well with bulk SiO/sub 2/ behavior. Better agreement between measurement and finite element simulation of MOSFET thermal resistance is obtained by using these extracted thermal conductivity values. It is also shown that the role of the silicon substrate in determining the thermal resistance of the device can be calculated using a simple analytical model. This is important when one wishes to calculate accurately individual thermal resistances of transistors in a given circuit.

A fully integrated VCO at 2 GHz

A fully integrated voltage-controlled oscillator at a frequency of 2 GHz with low phase noise has been implemented in a standard bipolar process with a f/sub t/ of 25 GHz. The design is based on an LC-resonator with vertical-coupled inductors. Only two metal layers have been used. The supply voltage of the oscillator is 2.7 V. The phase noise is only -136 dB/Hz at 4.7 MHz frequency offset. A tuning range of 150 MHz is achieved with integrated tuning diodes.

Two silicon optical modulators realizable with a fully compatible bipolar process

In this paper, we describe two different kinds of silicon optical modulators both integrated into a silicon on silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III-V optoelectronics. The first device presented is based on a three-terminal active device and exploits the plasma dispersion effect to achieve the desired modulation. The active device used is a bipolar mode field effect transistor; we show how the introduction of the third control terminal introduces some definite advantages with respect to commonly p-i-n driven modulators. The second is an electrically controlled Bragg reflector. In this case, although controlled by a p-i-n diode, fast switching speed is achieved. because lower injection levels are required. Numerical simulations and preliminary experimental results are presented on both devices.

An ultra-low-power, low-voltage electronic audio delay line for use in hearing aids

In this paper, the design of an electronic audio delay line, realized with a second-order all-pass filter, is presented. The designed filter is primarily intended for use in hearing aids, to provide directivity by a specially designed microphone array. The filter operates at a supply voltage of as low as 1.8 V. The simulated and measured total quiescent current is 0.9 /spl mu/A. Owing to current companding and class-AB operation, the dynamic range is 62 dB at a total harmonic distortion (THD) below 7%, i.e., at maximum output. The delay time is adjustable by control currents. The filter has been integrated in a standard bipolar process. The total measured delay time of the all-pass filter is approximately 110 /spl mu/s over a bandwidth of 4 kHz.

Stress control of piezoelectric ZnO films on silicon substrates

Piezoelectric zinc oxide (ZnO) films are widely used for the generation and detection of acoustic waves in non-piezoelectric substrates. The application of these films on silicon offers the possibility of realizing acoustic wave devices integrated with electronic circuits, e.g. sensors. It has been demonstrated that ZnO films can be combined with standard bipolar or CMOS IC processes. However, the stress in ZnO is still an important drawback and hinders the further development of silicon integrated acoustic wave devices, particularly if the ZnO layer is deposited on thin membranes, e.g. Lamb wave devices. In this paper we discuss aspects of stress in ZnO, methods to prevent or reduce the stress and we describe an IC-compatible method for the determination of the stress in ZnO films deposited on 100 mm diameter silicon wafers.

A VLSI-compatible high-speed silicon photodetector for optical data link applications

A novel silicon photodetector suitable for high-speed, low-voltage operation at 780- to 850-nm wavelengths is reported. It consists of an interdigitated p-i-n detector fabricated on a silicon-on-insulator (SOI) substrate by using a standard bipolar process. Biased at 3.5 V, this device attains a -3-dB bandwidth in excess of 1 GHz at /spl lambda/=840 nm. The dc responsivity measured at /spl lambda/=840 nm on nonoptimized structures ranges from 0.05 to 0.09 A/W, depending on the finger shadowing factor. A new approach for improving the responsivity is proposed and quantitatively analyzed. The fabricated devices exhibit extremely low dark currents, small capacitance, large dynamic range, and no evidence of low-frequency gain. The overall performance and process compatibility of these photodetectors make them viable candidates for the fabrication of silicon monolithic receivers for fiber-optic data links.

High tolerance to radiation effects and low noise performance of ACUTE-a complementary bipolar SOI IC technology

The 1/f noise performance of advanced complementary bipolar process from united technologies (ACUTE) is presented as a function of total dose, device geometry, and polarity as well as bias condition during irradiation. ACUTE's noise performance is also compared to noise from devices built on a standard bipolar process. The measured noise spectrum is expressed in terms of Hooge's constant-/spl alpha//sub H/ which normalizes the "noisiness" of the device to its geometry and doping profiles and therefore allows one to compare different structures. The results indicate a significant radiation tolerance and superior low noise of ACUTE process as compared with standard bipolar technology.

A low-cost multichannel optical transmission system for video signals

A novel low-cost multichannel optical transmission system for video signals is described. The system uses time-division multiplex pulse-position modulation (TDPPM). The transmitter and receiver are realized in a standard bipolar process while an external low-cost laser and PIN photodiode are used. A maximum of 16 channels can be multiplexed, while achieving a weighted signal-to-noise ratio (SNR) of 54 dB, a differential gain of 1% and a differential phase of 0.5/spl deg/. For a launched power of 0 dBm (pulse amplitude), the optical budget for a 45 dB weighted SNR exceeds 20 dB. Besides video signals the system is also capable of handling other signals such as digital coded audio signals or computer data. The feasibility of a four-channel system has been confirmed by measurements. >

Fabrication compatibility of integrated silicon smart physical sensors

Integrated silicon smart sensors are complete data-acquisition systems on a single silicon chip. The celebrated material compatibility of silicon sensors with microelectronic circuits in silicon is a necessary but insufficient prerequisite for such an integration. The essential issue is rather the fabrication compatibility of the sensor, sensor-related analog microelectronic circuits and digital interface circuits. Fabrication compatibility includes merging of sensor processing with analog and digital microelectronic circuit processing, both on the wafer level, in terms of doping profile, thermal budget and equipment utilization, and on the die level, with respect to testing, dicing, bonding and packaging. The incentives, opportunities and problems in merging sensor processes with a typical standard bipolar process are discussed. In some applications the structures to be merged are fundamentally fabrication incompatible. Special post-processing steps are available that either extend the capabilities of the bipolar process, such as selective epitaxial growth and epitaxial lateral overgrowth, or allow the fabrication-compatibility problem to be postponed until the bonding phase, such as wafer-to-wafer bonding and flip-chip bonding. Finally, the economics of integrated silicon smart sensors are investigated. The shortcomings of the conventional approach adopted from the microelectronics industry and aiming solely at die-area minimization, whenever possible for the sake of yield in mass production, are identified in view of fabrication compatibility, production volume and costs of testing and packaging. Moreover, the discrepancy between the prime motivation for fabricating integrated silicon smart sensors, namely enhancing the level of abstraction of the complete data-acquisition unit and its realization on the smallest possible material carrier, the chip, in order to improve user friendliness and maintainability in an effort to gain market acceptance, versus the limitation of functional complexity imposed by die-area economics is discussed.

An integrated optical position-sensitive detector with digital output and error correction

An integrated optical position-sensitive detector (PSD) with digital output is presented. A novel interpolating analog-to-digital converter which is based on a sigma-delta converter, is applied to perform three operations simultaneously. These are: calculation of the relative position cancellation of errors, both optical and electrical; generation of a microprocessor-compatible digital output. The realized smart sensor is integrated in a standard bipolar IC process, and measures 6.5 mm × 2.5 mm.

Piezoresistive accelerometer with overload protection and low cross-sensitivity

Abstract A piezoresistive silicon bridge-type accelerometer is described. The application of a standard bipolar process allows the mechanical structure to be realized by anisotropic wet etching in KOH with an electrochemical etchstop at selectively diffused n-type layers. A novel glass-bonding technology offers complete encapsulation of the sensor with silicon top and bottom caps, including wafer-level assembly and simultaneous overload protection. Optimization of the mechanical structure by finite-element modelling (FEM) with respect to the resonance frequency results in the application of transverse piezoresistors with excellent cross-sensitivity compensation. The sensor features a sensitivity of 40 μV/N g with a non-linearity of less than 0.5% up to 350 g, first resonance frequency of about 5 kHz, and cross-sensitivity in lateral directions of less than 0.2% with an overall chip size of 3.7 × 3.7 × 1.0 mm3.

A curvature-corrected low-voltage bandgap reference

A curvature-corrected bandgap reference that can function at supply voltages as low as 1 V, at a supply current of only 100 mu A, is presented. After trimming, this bandgap reference has a temperature coefficient (TC) of +or-4 p.p.m./ degrees C. The reference voltage is about 200 mV and it can easily be adjusted to higher values. The temperature range of this circuit is from 0 to 125 degrees C. This bandgap reference is realized using a standard bipolar process with base-diffused resistors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 2.5-V active low-pass filter using all-n-p-n Gilbert cells with a 1-V/sub p-p/ range

This paper describes the design and measured results of an all-n-p-n low-voltage (2.5 V), low-current (1 mA), large-swing (1 V/sub p-p/), low-distortion (-53 dB, 1 V/sub p-p/) active filter using a conventional bipolar process. The transconductors for the filter are composed of Gilbert cell transconductors. Distortion has been improved by feedback circuits without increasing the supply voltage and without using p-n-p transistors. The filter is a gyrator-capacitor type third-order Butterworth low-pass filter with a nominal cutoff frequency of 192 kHz. A voltage scaling technique has been applied directly to the gyrator-capacitor filter. This has improved the signal-to-noise ratio by 3 dB. Simulation results indicated that a fast operation up to tens of MHz is possible with a standard bipolar process, as the signal path is composed only of n-p-n transistors. >

Memory switching effects in a-Si/c-Si heterojunction bipolar structures

The authors report a three-terminal undoped amorphous silicon (a-Si)/p-n crystalline silicon (c-Si) structure, which exhibits OFF and ON states. An OFF state is characterized by a current in the structure in the low nanoampere range due to the large resistance of the undoped a-Si layer, while in the ON state the structure exhibits a large conductance and its current is determined in practice by the load resistance. Reversible switching between the two states with a rise time of about 40 ns and a fall time of about 200 ns was achieved by applying appropriate positive or negative current pulses to the base of the c-Si p-n junction. The structure can be integrated into a standard bipolar process, and, being of a size suitable for VLSI applications, may be useful as a basic three-terminal memory cell. >

Processing high-quality silicon for microstrip detectors

An investigation has been made into the behaviour of high-purity silicon (HP-Si) during the fabrication of microstrip detectors. The resistivity of the silicon used is 3 kΩcm. The investigation is centred on standard bipolar processes based on ion implantation. It is found that, comparing the processes used, the best diode characteristics are achieved when a heat treatment at 600 °C is used after the ion-implantation step, whereas the worst results from an implantation and a 900 °C heat treatment. Thus it is shown that if integration of the electronic circuitry and the detector on a single chip is required, then the high-temperature heat treatments must be done before the ion-implantation step needed for detector fabrication.

Silicon magnetic field sensor with frequency output

An integrated silicon magnetic field sensor with frequency output and adapted to fields parallel to the chip surface is presented. The frequency output is based on two I 2L ring oscillators. The magnetic sensitivity is achieved by a Hall-effect modulated difference in the currents injected by the transistor current sources of each ring oscillator. For the generation of a Hall potential in response to a lateral magnetic field, a new bipolar Hall element is designed. The device has two equivalent current paths with a current flow parallel to the chip surface. Various types of these devices with different geometrical data are fabricated using a standard bipolar process suitable for I 2L. The measurement results presented deal with the primary Hall-effect devices, the analog intermediate stage including the transistors, and the sensor with frequency output.