Chun-Tsen Lu

Characteristics of Pd/InGaP Schottky diodes hydrogen sensors

Pd/InGaP hydrogen sensors based on the metal-oxide-semiconductor (MOS) and metal-semiconductor Schottky diodes have been fabricated and systematically studied. The effects of hydrogen adsorption on device performances such as the current-voltage characteristics, barrier height variation, hydrogen coverage, and heat of adsorption are investigated. The studied devices exhibit very wide hydrogen concentration detection regimes and remarkable hydrogen-sensing properties. Particularly, an extremely low hydrogen concentration of 15 ppm H/sub 2//air at room temperature can be detected. In addition, under the presence of oxide layers in the studied MOS device structure, the enhancements of barrier height and high-temperature operating capability are observed. The initial heat of adsorption for Pd/oxide and Pd/semiconductor interface are calculated as 355 and 65.9 meV/atom, respectively. Furthermore, the considerably short response times are found in studied devices.

A new Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor

A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated.

A new Pt/oxide/In/sub 0.49/Ga/sub 0.51/P MOS Schottky diode hydrogen sensor

A new and interesting Pt/oxide/In/sub 0.49/Ga/sub 0.51/P metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations and at different temperatures are measured. The presence of dipoles at the oxide layer leads to an extra electrical field and the variation of Schottky barrier height. Even at room temperature, a very high hydrogen detection sensitivity of 561% is obtained when a 9090 ppm H/sub 2//air gas is introduced. In addition, an absorption response time less than 1 s under the applied voltage of 0.7 V and 9090 ppm H/sub 2//air hydrogen ambient is found. The roles of hydrogen adsorption and desorption for the transient response at different temperatures are also investigated.

Characteristics of a new Pt/oxide/In0.49Ga0.51P hydrogen-sensing Schottky diode

A new Pt/oxide/InGaP metal-oxide semiconductor (MOS) Schottky diode has been fabricated and studied. Upon exposure to hydrogen, the steady-state and transient responses under different hydrogen concentrations and temperatures are measured. Due to the inherent property of InGaP material, e.g. the wide energy gap, a wide hydrogen-sensing range as large as 300 K (from room temperature to 600 K) is obtained. Even at room temperature, a very high sensitivity over 500% for 9090 ppm hydrogen in air is acquired. Furthermore, the measured absorption response time is less than 1 s at the applied voltage of 0.7 V and 9090 ppm hydrogen concentration atmosphere condition. Simultaneously, based on the analysis of the variation of barrier height and hydrogen coverage, the characteristics of the studied Pt/oxide/InGaP MOS Schottky diode is in good agreement with the Lundstrom isotherm.

A hydrogen sensing Pd/InGaP metal-semiconductor (MS) Schottky diode hydrogen sensor

An interesting hydrogen sensing Pd/InGaP metal-semiconductor (MS) Schottky diode has been fabricated and studied. Both the steady state and the transient condition of the hydrogen adsorption process are investigated. Even at room temperature, an extremely low hydrogen concentration of 15 ppm H2/air can be detected. In addition, the wide operating temperature range of 250 K of the studied Pd/InGaP hydrogen sensor is found. From experimental results, it is shown that the variation of Schottky barrier height increases with the increase of the operating temperature and hydrogen concentration. As the operation temperature is elevated, the water formation effect is also studied in the quasi-equilibrium region under the transient condition.

A 3-10GHz Broadband CMOS T/R Switch for UWB Applications

A 3-10 GHz broadband CMOS T/R switch for ultra-wideband (UWB) transceiver is presented. The broadband CMOS T/R switch is fabricated based on the 0.18 mu 1P6M standard CMOS process. On-chip measurement of the CMOS T/R switch is performed. The insertion loss of the proposed CMOS T/R Switch is about 3.1plusmn1.3dB. The return losses at both input and output terminals are higher than 14 dB. It is also characterized with 25-34dB isolation and 18-20 dBm input P1dB. The broadband CMOS T/R switch shows highly linear phase and group delay of 20plusmn10 ps from 10MHz to 15GHz. It can be easily integrated with other CMOS RFICs to form on-chip transceivers for various UWB applications

A comprehensive study of polysilicon resistors for CMOS ULSI applications

Abstract The characteristics of polysilicon resistors for CMOS ULSI applications have been investigated. Based on the presented sub-quarter micron CMOS borderless contact, both n+ and p+ polysilicon resistors with Ti- and Co-silicide self-aligned process are used at the ends of each resistor. A simple and useful model is proposed to analyse and calculate some important parameters of polysilicon resistors including electrical delta W(ΔW), interface resistance Rinterface, and pure sheet resistance Rpure. Furthermore, the characteristics of voltage-coefficient resistor, temperature-coefficient resistor, and resistor mismatching are also studied. An interesting sine-wave voltage-dependent characteristic due to the strong relation to the Rinterface has been modelled in this paper. This approach can substantially help engineers in designing and fabricating the precise polysilicon resistors in sub-quarter micron CMOS ULSI technology.

Comparative hydrogen sensing performances of Pd– and Pt–InGaP metal–oxide–semiconductor Schottky diodes

The hydrogen sensing performances of Pd– and Pt–InGaP metal–oxide–semiconductor (MOS) Schottky diodes are systematically studied and compared under different operating temperature. It is known that, from experimental results, the Pd–InGaP MOS Schottky diode exhibits higher hydrogen detecting capability at lower hydrogen concentration regimes. On the contrary, the MOS Schottky diode with Pt catalytic material shows better hydrogen detecting capability and higher operating temperature. It is believed that the refractory Pt metal is responsible for detecting high hydrogen concentration in air, especially at high operating temperature. Furthermore, the temperature dependence of equilibrium constants is investigated and reported. In order to study the steady-state reaction kinetics, the van’t Hoff equation is used to estimate the values of initial heat of adsorption for both devices. Based on the Temkin isotherm model, the experimental results and theoretical simulation of hydrogen coverage are also studied an...

Comparative study of double ion implant Ti–salicide and pre-amorphization implant Co–salicide for ultra-large-scale integration applications

We have investigated the interesting double ion implant (DII) Ti–salicide and pre-amorphization implant (PAI) Co–salicide techniques for ultra-large-scale integration (ULSI) applications. The DII technique is combined with germanium (or arsenic) PAI and Si ion-mixing processes. The sheet resistances both of n+ and p+ polysilicons are decreased when the DII Ti–salicide and PAI Co–salicide techniques are used. Moreover, the incomplete phase transformation of Ti–salicide is not observed in 0.2 μm wide polysilicon devices with the Ge DII process. Furthermore, the n+/p-well junction leakage current is reduced when the Si ion-mixing process is used. Experimentally, based on the studied DII Ti–salicide and PAI Co–salicide techniques, high-performance 0.2 μm CMOS devices have been successfully fabricated.