Liquid crystal display device and process of manufacture

A method of manufacturing a liquid crystal display device comprising a thin film transistor substrate which controls alignment of liquid crystal, the method comprising:

• forming a first layer formed of a copper film having a purity of at least 99.5% and a second layer formed of an alloy film containing copper as a main component in a successive manner to form a laminated film, for forming a scanning signal line and a gate electrode;
• forming a film made of silicon nitride which serves as a gate insulating film, and forming a semiconductor layer by forming an amorphous silicon film and an n−-amorphous silicon film in a successive manner;
• forming an image signal line, a drain electrode, and a source electrode, which are each formed of a metal film;
• forming a film made of silicon nitride serving as a protective insulating film, and opening a through hole in the protective insulating film and in the gate insulating film;
• and
• forming a transparent conductive film to complete a pixel electrode,
• wherein the laminated film of the first layer and the second layer is subjected to etching with an etchant having a pH in a range smaller than 7.0.

A method of manufacturing a in-plane-switching system liquid crystal display device comprising a thin film transistor substrate which controls alignment of liquid crystal, the method comprising:

• forming a transparent conductive film containing an indium oxide as a main component, a first layer formed of a copper film having a purity of at least 99.5%, and a second layer formed of an alloy film containing copper as a main component in a successive manner to form a laminated film, for forming a scanning signal line, a gate electrode, a common signal line, and a common electrode;
• forming a film made of silicon nitride serving as a gate insulating film, and forming a semiconductor layer by forming an amorphous silicon film and an n−-amorphous silicon film in a successive manner;
• forming a metal film for forming an image signal line, a drain electrode, and a source electrode;
• forming a film made of silicon nitride serving as a protective insulating film, and opening a through hole in the protective insulating film and in the gate insulating film;
• and
• forming the transparent conductive film to complete a pixel electrode,
• wherein the common electrode is a base of the first layer;
• and
• the first layer and the second layer are subjected to etching with an etchant having a pH within a range of 1.8 to 7.0.

A method of manufacturing a liquid crystal display device comprising a thin film transistor substrate which controls alignment of liquid crystal, the method comprising:

• forming a first layer formed of a copper film having a purity of at least 99.5% anda second layer formed of an alloy film containing copper as a main component in a successive manner to form a laminated film, for forming a scanning signal line and a gate electrode;
• forming a film made of silicon nitride which serves as a gate insulating film, and forming a semiconductor layer by forming an amorphous silicon film and an n−-amorphous silicon film in a successive manner;
• forming a metal film for forming an image signal line, a drain electrode, and a source electrode;
• forming a film made of silicon nitride which serves as a protective insulating film, and opening a through hole in the protective insulating film and in the gate insulating film;
• and
• forming a transparent conductive film to complete a pixel electrode,
• wherein the laminated film of the first layer and the second layer is subjected to etching with an etchant having a pH within a range of 7.0 to 14.0.