Improvement in Gate Dielectric Quality of Ultra Thin a: SiN:H MNS Capacitor by Hydrogen Etching of the Substrate

To extend the scaling limit of thermal SiO2, in the ultra thin regime when the direct tunneling current becomes significant, members of our group embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. Silicon nitride can be deposited using several CVD methods and its properties significantly depend on the method of deposition. Although these CVD methods can give good physical properties, the electrical properties of devices made with CVD silicon nitride show very poor performance related to very poor interface, poor stability, presence of large quantity of bulk traps and high gate leakage current. We have employed the rather newly developed Hot Wire Chemical Vapor Deposition (HWCVD) technique to develop the a:SiN:H material. From the results of large number of optimization experiments we propose the atomic hydrogen of the substrate surface prior to deposition to improve the quality of gate dielectric. Our preliminary results of these efforts show a five times improvement in the fixed charges and interface state density

Ultra-thin silicon nitride by hot wire chemical vapor deposition (HWCVD) for deep sub-micron CMOS technologies

Silicon nitride is considered a promising candidate to replace thermal oxide dielectrics, as the latter is reaching its scaling limits due to the excessive increase in the gate tunneling leakage current. The novel hot wire chemical vapor deposition (HWCVD) technique shows promise for gate quality silicon nitride film yields at 250 °C while maintaining their primary advantage of a higher dielectric constant of 7.1. In this paper we report the results of our efforts towards developing ultra-thin HWCVD silicon nitride as an advanced gate dielectric for the replacement of thermal gate oxides in future generations of ultra large scale integration (ULSI) devices

Nitrogen dilution effects on structural and electrical properties of hot-wire-deposited a-SiN:H films for deep-sub-micron CMOS technologies

Hot-wire chemical vapor-deposited silicon nitride is a potential dielectric material compared to glow-discharge-deposited material due to its lower hydrogen content. In several earlier publications we have demonstrated these aspects of the HWCVD nitride. However, to replace SiO2 with a-SiN:H as the gate dielectric, this material needs further improvement. In this paper we report the results of our efforts to achieve this through nitrogen dilution of the SiH4+NH3 gas mixture used for deposition. To understand the electrical behavior of these nitride films, we characterized the films by high-frequency capacitance–voltage (HFCV) and DC J–E measurements. We attempted to evolve a correlation between the breakdown strength, as determined from the J–E curves, and aspects such as the bond density, etching rate, deposition rate and refractive index. From these correlations, we infer that nitrogen dilution of the source gas mixture has a beneficial effect on the physical and electrical properties of the hot-wire a-SiN:H films. For the highest dilution, we obtained a breakdown voltage of 12 MV cm−1

Suppression of boron penetration by hot wire CVD polysilicon

In the current and future deep sub-micron technologies, boron penetration through the gate dielectric is a severe reliability concern for the dual gate CMOS technology. In this paper we report results of our attempts to exploit the potential of Hot Wire CVD (HWCVD) for depositing poly-Si gate for CMOS technology. The effect of grain size of poly-Si gate on boron penetration is studied by varying the poly-Si grain size through variation in the HWCVD parameters.© IEE