Method of forming a ferroelectric film and fabrication process of a semiconductor device having a ferroelectric film

A method of fabricating a semiconductor device, comprising the steps of:

• forming an active element on a substrate;
• forming an electrode over said substrate in electrical connection with said active element, said step of forming said lower electrode being conducted by using a material that takes a metal state in a reducing ambient and an oxide state in an oxidizing ambient for said lower electrode;
• depositing a ferroelectric film on a surface of said electrode by supplying gaseous sources of said ferroelectric film and an oxygen gas and by causing a decomposition of said gaseous sources at said surface of said electrode;
• and
• depositing an upper electrode on said ferroelectric film,
• said step of depositing said ferroelectric film being started with a preparation step in which the state of said surface of said electrode is controlled substantially to a critical point in which a state of said electrode changes from said metal state to said oxide state and from said oxide state to said metal state.

A method of realizing a critical state of oxidation-reduction reaction on the surface of a layer that takes a metal state in a reducing ambient and an oxide state in an oxidizing ambient and shows a catalytic action in the metal state, comprising the steps of:

• introducing said layer into a process space;
• supplying an oxidizing gas and a vapor of an organic solvent into said process space;
• and
• causing an oxidizing reaction and a reducing reaction on said surface of said layer in said process space,
• said oxidizing gas and said vapor being supplied into said furnace with a proportion set such that there is caused an equilibrium between an oxidation reaction caused by said oxidizing gas and a reducing reaction caused by said vapor on said surface of said layer.

A method of determining the state of an oxidation-reduction reaction taking place on a layer of a material that takes a metal state in a reducing ambient and an oxide state in an oxidizing ambient, said material showing a catalytic action in said metal state, said method comprising the steps of:

• introducing said layer into a process space;
• supplying an oxidizing gas and a vapor of an organic solvent into said process space;
• causing an oxidizing reaction and a reducing reaction on said surface of said layer in said process space;
• examining a state of said surface of said layer;
• and
• determining a ratio of said oxidizing gas and said reducing gas that provides an equilibrium condition in which an oxidizing reaction and a reducing reaction equilibrate.

An apparatus for forming a ferroelectric film, comprising:

• a reactor evacuated by a pump;
• a stage provided in said reactor for holding a substrate;
• a first source supplying an oxidizing gas to said reactor;
• a second source supplying a reducing gas to said reactor;
• a third source supplying a gaseous source material of said ferroelectric film to said reactor;
• a detector detecting an oxide film formed on said substrate on said stage;
• and
• a controller controlling said first through third sources,
• said controller controlling said first and second sources in response to an output of said detector such that there is realized a critical state of oxidation-reduction reaction taking place on a surface of said substrate.