Peter K. McLarty

Single-wafer cluster tool performance: an analysis of throughput

Cluster tools gained greater acceptance over the past several years, although concerns still exist over the throughput these tools can achieve. This paper presents an analysis of the relationship between process times, transport times, and maximum throughput in an individual cluster tool. Theoretical models which quantify the time required to process both an individual wafer and a lot in a cluster tool are developed. Three techniques for increasing throughput, based on these models, are also presented. These modifications require minimal modification of many existing designs and can yield significant increases in performance. >

Modeled tunnel currents for high dielectric constant dielectrics

The effect of dielectric constant and barrier height on the WKB modeled tunnel currents of MOS capacitors with effective oxide thickness of 2.0 nm is described. We first present the WKB numerical model used to determine the tunneling currents. The results of this model indicate that alternative dielectrics with higher dielectric constants show lower tunneling currents than SiO/sub 2/ at expected operating voltages. The results of SiO/sub 2//alternative dielectric stacks indicate currents which are asymmetric with electric field direction. The tunneling current of these stacks at low biases decreases with decreasing SiO/sub 2/ thickness. Furthermore, as the dielectric constant of an insulator increased, the effect of a thin layer of SiO/sub 2/ on the current characteristics of the dielectric stack increases.

Silicon-carbide high-voltage (400 V) Schottky barrier diodes

The authors describe the fabrication and characteristics of the first high-voltage (400-V) silicon-carbide (6H-SiC) Schottky barrier diodes. Measurements of the forward I-V characteristics of these diodes demonstrate a low forward voltage drop of approximately 1.1 V at an on-state current density of 100 A/cm/sup 2/ for a temperature range of 25 to 200 degrees C. The reverse I-V characteristics of these devices exhibit a sharp breakdown, with breakdown voltages exceeding 400 V at 25 degrees C. In addition, these diodes are shown to have superior reverse recovery characteristics when compared with high-speed silicon P-i-N rectifiers.<<ETX>>

Single-wafer cluster tool performance: an analysis of the effects of redundant chambers and revisitation sequences on throughput

Recent trends in the semiconductor industry indicate the need to explore alternatives to batch-wafer manufacturing. One proposed alternative is a micro-factory based on cluster tools. This paper presents an analysis of the effect of redundant chambers and chamber revisitation process sequences on the throughput in an individual cluster tool. Theoretical models which quantify the time required to process a lot of wafers in a cluster tool are developed for these situations. The differences between scheduling algorithms which use the load-lock as a queue and those that do not are also explored. Finally, the models developed in the work are integrated into a model which bounds the minimum theoretical turn-around-time which can be achieved in a cluster based fab.

Electrical characteristics of epitaxial CeO2 on Si(111)

Electrical properties of epitaxial CeO2 thin films on silicon (111) substrates grown in ultrahigh vacuum were studied, varying growth conditions and ex situ thermal treatments. Characterization using reflection high‐energy electron diffraction and high resolution transmission electron microscopy reveal that while the ceramic layers have a good single‐crystal structure, a dual amorphous layer of CeOx and SiO2 forms at the CeO2/Si interface. This structure has undesirable electrical properties, however, utilizing a post‐anneal in dry oxygen, the α‐CeOx layer was removed and the SiO2 amorphous layer was made thicker. This newly developed structure benefits from the SiO2/Si interface, having Dit=6×1011 cm−2, and Qf=5×1011 cm−2. The structure exhibits a high capacitance due to the large dielectric constant of CeO2, has electrical properties comparable with those of other reported gate insulators on Si, and has an epitaxial oxide lattice matched to Si.

Electrical properties of thermal oxide grown on n‐type 6H‐silicon carbide

Measurement of current conduction in the metal/thermal oxide/n‐type 6H‐silicon carbide is reported. The thermal oxides were grown on nitrogen‐doped n‐type 6H‐silicon carbide at 1275 °C in a dry oxygen ambient. Analysis indicates a Fowler–Nordheim type current conduction mechanism with a barrier height of 2.7 eV between silicon carbide and oxide. Using this value an electron affinity of 3.7–3.8 eV was determined for the Si face of 6H‐silicon carbide. The breakdown field strength for the oxides grown on n‐type 6H‐silicon carbide was 10 MV/cm which is comparable to the breakdown field strength of thermal oxides grown on silicon. Capacitance‐voltage measurements indicated that the interface between n‐type silicon carbide and the thermally grown oxide has a low (5×1010 cm−2 eV−1) interface trap density (Dit). The effective charge density in the oxide was estimated to be 1×1011 cm−2. These measurements indicate that the quality of oxides thermally grown on 6H‐silicon carbide is comparable to those grown on silicon.

A simple edge termination for silicon carbide devices with nearly ideal breakdown voltage

In this paper, a simple edge termination is described which can achieve near ideal parallel plane breakdown for silicon carbide devices. This novel edge termination involves self aligned implantation of a neutral species on the edges of devices to form an amorphous layer. With this termination formed using argon implantation, the breakdown voltage of Schottky barrier diodes was measured to be very close to ideal plane parallel breakdown voltage.<<ETX>>

A simple parameter extraction method for ultra-thin oxide MOSFETs

Abstract A simple parameter extraction technique is presented for ultra-thin oxide MOSFETs. The technique is based on a suitable MOSFET mobility model and extracts threshold voltage ( V t ), mobility ( μ 0 ), and two mobility degradation parameters θ 1 and θ 2 . It has been found that the extracted parameters accurately describe the measured current voltage characteristics for strong inversion.

Low-pressure rapid thermal chemical vapor deposition of oxynitride gate dielectrics for n-channel and p-channel MOSFETs

The properties of oxynitride gate dielectrics formed using a low-pressure, rapid thermal chemical vapor deposition (RTCVD) process with SiH/sub 4/, NH/sub 3/, and N/sub 2/O as the reactive gases are presented. Material analyses show an increase of uniform nitrogen and interfacial hydrogen content with increasing NH/sub 3//N/sub 2/O flow rate ratio. MOS capacitors with both n-type and p-type substrates and both n-channel and p-channel MOSFETs were analyzed electrically. The results show increasing fixed oxide charge and interface state density with increasing nitrogen and hydrogen content in the film. A decrease in peak transconductance and improved high-field transconductance was observed for n-channel MOSFETs. Improved resistance to hot-carrier interface state generation was also observed with increasing nitrogen concentration in the films. The results suggest that an optimal nitrogen concentration of approximately 3 at.% can be considered for further development of this technology.

Low-frequency noise characterization of n- and p-MOSFET's with ultrathin oxynitride gate films

MOSFETs with ultrathin (5 to 8.5 nm) silicon oxynitride gate film prepared by low-pressure rapid thermal chemical vapor deposition (RTCVD) using SiH/sub 4/, N/sub 2/O and NH/sub 3/ gases, are studied by low-frequency noise measurements (1 Hz up to 5 kHz). The analysis takes into account the correlated mobility fluctuations induced by those of the interfacial oxide charge. The nitrogen concentration, determined from SIMS analysis, varies from 0 to 11% atomic percentage. A comparison of the electrical properties between thermal and silicon oxynitride films is presented. The increasing LF noise signal with nitrogen atomic percentage indicates the presence of a higher density of slow interface traps with increasing nitrogen incorporation. Besides, a higher Coulomb scattering rate due to the nitridation induced interface charge explains reasonably well the degradation of the low field mobility after nitridation.