Abstract
By in-situ transmission electron microscopy (TEM), we performed a detailed study on the electron-beam radiation damage to nanostructured silicon nitride thin-film process layers in a typical semiconductor NVM device. It was found that high-dose electron-beam radiation at 200 kV led to rapid degradation of silicon nitride process layers, i.e. thin-downing of nanostructured silicon nitride, inter-diffusion of O and N, the formation of bubble-like defects and segregation of N at neighbouring interfaces. Further detailed analysis revealed that radiation-induced modification in the microstructure and chemical composition of silicon nitride layers could be ascribed to the electron radiation induced knock-on damage and ionization damage. The radiation enhanced diffusion (RED) accounted for the continuous thin-down of the nitride process layer and the formation of bubble-like defects in thick nitride spacer process layers. The work well demonstrated the electron-beam sensitivity of nanostructured silicon nitride materials in the semiconductor devices, and thus may give useful information about electron-dose control during TEM failure analysis of the semiconductor devices containing nanostructured silicon nitride process layers.
Highlights
Since the early semiconductor development, silicon nitride (SixNy) by chemical vapour deposition (CVD) techniques has been widely used for various process layers and for various purposes in semiconductor devices
The results are in line with the studies reported for the different material systems such as CoFe,[14] C,19 CoFeB,[26] in which it was generally accepted that electron radiation induced temperature increment could be ignored
The results indicated that high-dose electron radiation can result in fast radiation damage to silicon nitride thin film process layers with the modification of both microstructure and chemical composition of silicon nitride
Summary
Since the early semiconductor development, silicon nitride (SixNy) by chemical vapour deposition (CVD) techniques has been widely used for various process layers and for various purposes in semiconductor devices. In both floating-gate based and nitride-based NVM devices, the nitride process layer by CVD is the indispensable structure. In order to understand the electron-beam sensitivity of nanostructured silicon nitride thin films in semiconductor devices, we present detailed electron-beam radiation study on a typical ONO structure in a sub-65nm NVM device by in-situ TEM As it is well known, for sub-65nm CMOS processes, the control of thermal budget during front-end-of-line processes is crucial to achieve desirable device performance, for which the thin film deposition normally utilizes low-temperature CVD processes, including the nitride thin film process layers in the embedded NVM devices in this study. The work may give useful information about the electron-beam sensitivity of silicon nitride materials, and the importance of electron-dose control during the TEM failure analysis of semiconductor devices with nitride process layers
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