Semiconductor memory device and method for manufacturing semiconductor device

Abstract

After a lower silicon oxide film is formed on a silicon region, a silicon film is formed on the lower silicon oxide film by, for example, a thermal CVD method. Subsequently, the silicon film is completely nitrided by a plasma nitriding method to be replaced by a silicon nitride film. Subsequently, a surface layer of the silicon nitride film is oxidized by a plasma oxidizing method to be replaced by an upper silicon oxide film. An ONO film as a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film, and the upper silicon oxide film is formed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a division of application Ser. No. 10 / 643,967 filed Aug. 20, 2003, based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-256195, filed on Aug. 30, 2002, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method for manufacturing a semiconductor device having a gate insulation film or a dielectric film including a nitrided film, and a semiconductor memory device capable of holding information by storing electric charges in the nitrided film. [0004] 2. Description of the Related Art [0005] Recently, an ON film composed of a silicon nitride film formed on a silicon oxide film, and an ONO film composed of a silicon oxide film, a silicon nitride film, and a silicon oxide film formed in this order are used for a memory cell of a semiconductor memory device. [0006...

AI Technical Summary

Benefits of technology

"The present invention provides a method for manufacturing a semiconductor device and a semiconductor memory device with high reliability by forming a multilayered insulating film such as an ON film, an ONO film, or the like in low temperature and of high quality. The method includes steps of forming a lower silicon oxide film, a silicon film on the lower silicon oxide film, and a silicon nitride film on the lower silicon oxide film to completely nitride the silicon film by a plasma nitriding method, resulting in a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film, and an upper silicon oxide film. The semiconductor memory device includes a memory cell with a silicon nitride film having a charge-capture function formed by only plasma nitriding through microwave excitation or a series of processing including the plasma nitriding. The method and device provide improved reliability and performance of semiconductor devices and memory devices."

Problems solved by technology

Recently, a tendency toward a demand for miniaturization and high performance of a semiconductor memory has been further increasing, and accordingly, the following serious problems regarding formation of the multilayered insulating film have been raised.

However, since heat treatment with a high temperature and long hours is required, the hydrogen entrapped in the silicon nitride film is diffused and passes into the lower silicon oxide film.

It is clear that the passing of the hydrogen into the lower silicon oxide film causes deterioration of a film quality of the lower silicon oxide film.

Since high temperature is required for forming the multilayered insulating film, the hydrogen reaches the lower silicon oxide film through the floating gate, resulting in deterioration of quality of the lower silicon oxide film as the tunnel oxide film.

However, the impurities of the well are thermally diffused by the aforementioned processing at high temperature, resulting in difficulty in miniaturization of the element.

Especially, in a memory having sources / drains also serving as embedded bit lines, when the sources / drains are formed after the multilayered insulating film is formed in order to prevent thermal diffusion of the impurities caused by the processing at high temperature, a defect occurs in the multilayered insulating film by ion implantations of the impurities, causing such a problem as increase in leakage current or decrease in reliability.

This makes a current situation that a semiconductor memory of high performance is difficult to be realized.

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