High-quality hydrogen-diluted a-SiN x :H films deposited by hot-wire chemical vapor deposition
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High-quality hydrogen-diluted a-SiNx:H films deposited by hot-wire chemical vapor deposition Fengzhen Liu,1a Lynn Gedvilas,1 Brian Keyes,1 Errol Sanchez,2 Shulin Wang,2 and Qi Wang1b 1 National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA 2 Applied Materials, Inc., 979 E. Argues Ave., Sunnyvale, CA 94086, USA a : Current address: Physics Department, Graduate School, Chinese Academy of Sciences, Beijing 100039, China b : Contact email: [email protected] Abstract We have studied the effect of H dilution on silicon nitride films deposited by the hot-wire chemical vapor deposition (HWCVD) technique using SiH4, NH3, and H2 gases. We found that H dilution significantly enhances the properties at silicon nitride films. The N content in the film increases by more than 2 times compared to the film without dilution, based on FTIR measurements. As a result, we can achieve high-quality a-SiNx:H films at low substrate temperature using a much lower gas ratio of NH3/SiH4 (~1) compared to a ratio of about 100 for conventional deposition by HWCVD. We also found that dilution decreases the H content in the films. More importantly, diluted SiNx films are conformal. Scanning electron microscopy measurements show a nearly 100% surface coverage over a sharp object. Electric breakdown measurement shows a well-insulated film with more then a few MV/cm for the breakdown field. Introduction Silicon nitride thin films have been widely used in the semiconductor industry and in large-area electronics applications. These films are often used for surface passivation for crystal Si (c-Si) applications, antireflection coating, dielectric layers for thin-film transistors, water- resistive coating, and conformal coverage in microelectronics [1-5]. Recently, silicon nitride on plastic has attained a unique position as the moisture resistance layer for many bio-applications [6]. The HWCVD technique has the advantage of low processing temperatures from 25° to 350°C, no ions or plasma-related damage, and high deposition rates compared to other silicon nitride deposition methods such as plasma-enhanced (PE) CVD, atomic layer deposition, and thermal CVD. Several research groups [1, 7-9] are leading the efforts to study HWCVD silicon nitride thin films. In comparing the deposition parameters among other research groups, we found that most groups use a high NH3/SiH4 flow ratio for the deposition of highquality amorphous silicon nitride (a-SiNx:H) film. The properties of those high-ratio aSiNx:H films are very promising in many aspects except for the conformal coverage. We have studied HWCVD silicon nitride films with a different approach [9]. We found that adding H2 to the process, and using high filament temperature and high pressure significantly simplify the process and enhance silicon nitride film properties. We used a rather small ratio of NH3/SiH4 and, more importantly, a silicon nitride film with complete
A9.23.2
conformal coverage has been achieved. In this paper, we report the results of our studies of the influenc
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