Ferroelectric device and method for manufacturing same

Abstract

A ferroelectric device and a manufacturing method are provided. While holding a nonvolatile memory retention capability and a multiple rewriting endurance as the distinctive features of a ferroelectric device, the disclosed ferroelectric device is wider in memory window and more adaptively made microfiner than a conventional ferroelectric device that has used a ferroelectric mainly constituted of Sr—Bi—Ta—O as an oxide of strontium, bismuth and tantalum. Directly on or with intermediary of an insulator on a semiconductor there are layered a first ferroelectric and a conductor to form a gate stack, the first ferroelectric being mainly constituted of Sr—Ca—Bi—Ta—O as an oxide of strontium, calcium, bismuth and tantalum and being built up by a metal organic vapor deposition technique from a suitable film-forming raw material. The gate stack is heat-treated to cause the first ferroelectric to develop its ferroelectricity.

1 . A method of making a ferroelectric device having a semiconductor on which there is a multi-layered structure having an insulator, a ferroelectric and a conductor built up in this order or a multi-layered structure having a ferroelectric and a conductor built up in this order, the method being characterized in that it comprises making a layer of said ferroelectric by a metal organic chemical vapor deposition process which comprises the steps of: preparing a raw material liquid solution having complex compounds each dissolved in a solvent, the complex compounds containing strontium, calcium, bismuth and tantalum; dispersing the raw material liquid solution into a carrier gas to form a raw material gaseous medium in a state of gas and liquid two phases; introducing the raw material gaseous medium while in the state of gas and liquid two phases into a vaporizing chamber to form a vapor thereof; and introducing the vapor into a film forming chamber; wherein the complex compound is Ca[Ta(OC 2 H 5 ) 5 (OC 2 H 4 OCH 3 )] 2 . 
     
     
         2 . A method of making a ferroelectric device as set force in  claim 1 , wherein the ferroelectric device has a gate stack structure having an insulator, a ferroelectric and a conductor built up in this order, or a gate stack structure having a ferroelectric and a conductor built up in this order on a semiconductor having source, channel and drain regions. 
     
     
         3 . A method of making a ferroelectric device as set force in  claim 1 , wherein the metal organic chemical vapor deposition process comprises: dispersing the raw material liquid solutions into a carrier gas to form a raw material gaseous medium in a state of gas and liquid two phases; introducing the raw material gaseous medium while in the state of gas and liquid two phases into a vaporizing chamber to form a vapor thereof; and introducing the vapor into a film forming chamber. 
     
     
         4 . A method of making a ferroelectric device as set force in  claim 2 , wherein the metal organic chemical vapor deposition process comprises: dispersing the raw material liquid solutions into a carrier gas to form a raw material gaseous medium in a state of gas and liquid two phases; introducing the raw material gaseous medium while in the state of gas and liquid two phases into a vaporizing chamber to form a vapor thereof; and introducing the vapor into a film forming chamber. 
     
     
         5 . A ferroelectric device characterized in that it comprises a semiconductor on which there is a multi-layered structure having an insulator, a ferroelectric and a conductor built up in this order or a multi-layered structure having a ferroelectric and a conductor built up in this order, wherein the ferroelectric contains strontium, calcium, bismuth and tantalum, and is made by a metal organic chemical vapor deposition process using Ca[Ta(OC 2 H 5 ) 5 (OC 2 H 4 OCH 3 )] 2  as a raw material. 
     
     
         6 . A ferroelectric device as set force in  claim 5 , wherein the ferroelectric device has a gate stack structure having an insulator, a ferroelectric and a conductor built up in this order, or a gate stack structure having a ferroelectric and a conductor built up in this order on a semiconductor having source, channel and drain regions. 
     
     
         7 . A ferroelectric device as set force in  claim 5 , wherein the metal organic chemical vapor deposition process comprises: dispersing the raw material liquid solutions into a carrier gas to form a raw material gaseous medium in a state of gas and liquid two phases; introducing the raw material gaseous medium while in the state of gas and liquid two phases into a vaporizing chamber to form a vapor thereof; and introducing the vapor into a film forming chamber. 
     
     
         8 . A ferroelectric device as set force in  claim 6 , wherein the metal organic chemical vapor deposition process comprises: dispersing the raw material liquid solutions into a carrier gas to form a raw material gaseous medium in a state of gas and liquid two phases; introducing the raw material gaseous medium while in the state of gas and liquid two phases into a vaporizing chamber to form a vapor thereof; and introducing the vapor into a film forming chamber.