Ferroelectric capacitor and semiconductor device

Abstract

A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, is characterized in that said ferroelectric thin film is a perovskite-type oxide containing Pb and said upper and bottom electrodes contain an intermetallic compound composed of Pt and Pb. An electronic device is provided with said ferroelectric capacitor. This construction is designed to solve the following problems. In a non-volatile ferroelectric memory (FeRAM), a degraded layer occurs near the interface between the PZT and the electrode due to hydrogen evolved during processing or due to diffusion of Pb from the PZT into the electrode. A stress due to a difference in lattice constant occurs in the interface between the electrode and the ferroelectric thin film. The degraded layer and the interfacial stress deteriorate the initial polarizing characteristics of the ferroelectric capacitor and also greatly deteriorate the polarizing characteristics after switching cycles.

1 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that said ferroelectric thin film is a perovskite-type oxide containing a metal element and said top electrode contains an intermetallic compound composed of said metal element and a noble metal.  
     
     
         2 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that said ferroelectric thin film is a perovskite-type oxide containing a metal element and said top electrode and bottom electrode contain an intermetallic compound composed of said metal element and a noble metal.  
     
     
         3 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that said ferroelectric thin film is a perovskite-type oxide containing a metal element, and at least either of said top electrode or said bottom electrode has a multilayer structure formed by sequentially laminating a layer containing an intermetallic compound composed of said metal element and a noble metal and a layer of said noble metal, the former being adjacent to the interface of the ferroelectric thin film.  
     
     
         4 . A ferroelectric capacitor of the type having a substrate, a buffer layer, a bottom electrode, and a ferroelectric thin film, which are sequentially laminated, characterized in that said buffer layer is made of a transition metal or a nitride thereof, said ferroelectric thin film is made of a perovskite-type oxide containing a metal element, and said bottom electrode contains an intermetallic compound composed of said metal element and a noble metal.  
     
     
         5 . A ferroelectric capacitor as defined in  claim 4 , in which said noble metal is Pt, said intermetallic compound is one which is composed of Pb and Pt, with the Pb content being 50 atom % or less, and said transition metal is Ti.  
     
     
         6 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that said ferroelectric thin film is made of a perovskite-type oxide containing a metal element and said top electrode is made of a substance composed of Pt and Pb in the range of 10 atom % to 50 atom %.  
     
     
         7 . A ferroelectric capacitor as defined in any of  claims 1  to  6 , in which said intermetallic compound is one which has a L 1   2  type crystal structure represented by the composition formula of Pt 3 Pb.  
     
     
         8 . A ferroelectric capacitor as defined in any of  claims 1  to  6 , in which said intermetallic compound is one which has a crystal structure based on a face centered cubic lattice.  
     
     
         9 . A ferroelectric capacitor as defined in any of  claims 1  to  6 , in which said bottom electrode has a crystal structure based on a face centered cubic lattice and orients mainly in the (111) plane, (100) plane, or (110) plane.  
     
     
         10 . A ferroelectric capacitor as defined in any of  claims 1  to  6 , in which both said ferroelectric thin film and said bottom electrode orient mainly in the (111) plane, (100) plane, or (110) plane.  
     
     
         11 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that said bottom electrode is of double layer structure composed of a first layer of metal having a face centered cubic lattice and a second layer of an alloy containing said metal, and the difference in lattice constant between said first layer and said second layer is 3.5% or less.  
     
     
         12 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that at least either of said top electrode or said bottom electrode has the basic structure of a face centered cubic lattice, and the difference in lattice constant between said bottom electrode and said ferroelectric thin film is 1% or less.  
     
     
         13 . A ferroelectric capacitor of the type having a top electrode, a ferroelectric thin film, and a bottom electrode, characterized in that at least either of said top electrode or said bottom electrode has the basic structure of a face centered cubic lattice, and the difference in lattice constant between said bottom electrode and said ferroelectric thin film is 1% or less.  
     
     
         14 . A ferroelectric capacitor as defined in any of  claims 1  to  6 , in which said ferroelectric thin film has a thickness of 1000 Å or less.  
     
     
         15 . A ferroelectric memory cell in which the ferroelectric capacitor defined in any of  claims 1  to  14  is formed on the gate of a semiconductor field effect transistor.  
     
     
         16 . A ferroelectric memory cell in which the ferroelectric capacitor defined in any of  claims 1  to  14  is formed as the capacitor of the semiconductor MOS part.  
     
     
         17 . A semiconductor device which has the ferroelectric memory cell defined in  claim 15  or  16 .  
     
     
         18 . A system LSI which has the ferroelectric memory cell defined in  claim 15  or  16 .  
     
     
         19 . An IC card which has the ferroelectric memory cell defined in  claim 15  or  16 .