Ferroelectric film, ferroelectric capacitor, ferroelectric memory, piezoelectric element, semiconductor element, method of manufacturing ferroelectric film, and method of manufacturing ferroelectric capacitor

Abstract

A ferroelectric film is formed by an oxide that is described by a general formula AB1-xNbxO3. An A element includes at least Pb, and a B element includes at least one of Zr, Ti, V, W, Hf and Ta. The ferroelectric film includes Nb within the range of: 0.05≦x<1. The ferroelectric film can be used for any of ferroelectric memories of 1T1C, 2T2C and simple matrix types.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional of application Ser. No. 092,800, filed Mar. 8, 2002, which application is incorporated herein by reference in its entirety. [0002] The disclosures of Japanese Patent Application No. 2002-309487, filed on Oct. 24, 2002, Japanese Patent Application No. 2003-76129, filed on Mar. 19, 2003, Japanese Patent Application No. 2003-85791, filed on Mar. 26, 2003, Japanese Patent Application No. 2003-294072 filed on Aug. 18, 2003, and Japanese Patent Application No. 2003-302900 filed on Aug. 27, 2003 are hereby incorporated by reference in their entirety.BACKGROUND OF THE INVENTION [0003] The present invention relates to a ferroelectric film, a ferroelectric capacitor, a ferroelectric memory, a piezoelectric element, a semiconductor element, a method of manufacturing a ferroelectric film, and a method of manufacturing a ferroelectric capacitor. [0004] It has recently become popular to perform research and development...

AI Technical Summary

Benefits of technology

The present invention provides a type of ferroelectric memory that can be used in different types of memory devices. The invention also provides a method for manufacturing the memory device using a specific ferroelectric film. The invention also includes a piezoelectric element and a semiconductor element that use the ferroelectric film. The invention provides a simple process for manufacturing the memory device without the need for a barrier film. The ferroelectric film has a general formula of AB1-xNbxO3, where A is Pb or another element, B is Zr, Ti, V, W, Hf, or Ta, and Nb is within a certain range.

Problems solved by technology

Of these, the structure of the 1T type leads to the generation of internal electrical fields which shorten the retention (data preservation) to one month, so it is thought to be impossible to provide a guarantee of ten years, which is generally requested of semiconductors.

For that reason, failures occur in the leakage current characteristic or imprint characteristic (measures of hysteresis distortion), making it difficult to ensure reliability.

PZT tetragonal crystals exhibit a hysteresis characteristic that has the squareness suitable for memory applications, but they lack reliability and cannot be used in practice.

In addition, static imprint testing in which data is written once in either the positive or negative direction and the memory device is heated and held at 100° C. has shown that most of the written data disappears after 24 hours.

These problems are intrinsic to the ionic crystals of PZT and to the Pb and Ti that are constituent elements of PZT, and create the greatest technical problem relating to PZT tetragonal thin film in which large proportions of the constituent elements are Pb and Ti.

This technical problems is great because PZT Perovskite is ionic crystals, and is intrinsic to PZT.

As shown in FIG. 45B, since oxygen ions appear in the vicinity of positive ions in the Brownmillerite type of crystal structure, positive ion defects make it difficult for excessive leakage current to increase.

In addition to the above-described generation of leakage currents, insufficiencies of Pb and Ti and the concomitant insufficiency of O, which are lattice defects, cause spatial charge polarization such as that shown in FIG. 46.

When that happens, reverse electrical fields due to lattice defects are created by the electrical fields of ferroelectric polarization can occur, causing a state in which the bias potential is impeded in the PZT crystals, and hysteresis shift or collapse can occur as a result.

The above problems are intrinsic to PZT and it is considered difficult to analyze these problems in pure PZT, so that up until now it has not been possible to implement suitable characteristics for a memory element made by using tetragonal PZT.

Since the ferroelectric film at this point is mainly formed of oxides, the oxides are reduced by the generated hydrogen during the fabrication process, which has an undesirable effect on the characteristics of the ferroelectric capacitor.

Images