Etching method and method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a stacked semiconductor film including a crystalline semiconductor film and an amorphous semiconductor film over the crystalline semiconductor film;
• forming an etching mask over a first region of the stacked semiconductor film;
• and
• performing a first etching and a second etching on a second region of the stacked semiconductor film to expose a part of the crystalline semiconductor film,
• wherein the first etching is performed using a first gas including a CF4 gas, and
• wherein the second etching is performed using a second gas including an HBr gas, a CF4 gas and an oxygen gas.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first conductive layer over a substrate;
• forming a first insulating film over the first conductive layer;
• forming a crystalline semiconductor film over the first insulating film;
• forming an amorphous semiconductor film over the crystalline semiconductor film;
• forming an impurity semiconductor film over the amorphous semiconductor film;
• etching a portion of the crystalline semiconductor film, the amorphous semiconductor film and the impurity semiconductor film to form a thin film stack;
• forming a conductive film over the thin film stack;
• etching the conductive film to form a second conductive layer;
• and
• performing a first etching and a second etching on the thin film stack in a portion which does not overlap with the second conductive layer to expose the crystalline semiconductor film in the portion which does not overlap with the second conductive layer,
• wherein the first etching is performed using a first gas including a CF4 gas, and
• wherein the second etching is performed using a second gas including an HBr gas, a CF4 gas, and an oxygen gas.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film over the gate electrode;
• forming a crystalline semiconductor film over the gate insulating film;
• forming an amorphous semiconductor film over the crystalline semiconductor film;
• forming an impurity semiconductor film over the amorphous semiconductor film;
• forming a first etching mask over the impurity semiconductor film;
• etching a portion of the crystalline semiconductor film, the amorphous semiconductor film and the impurity semiconductor film which does not overlap with the first etching mask to form a thin film stack;
• removing the first etching mask;
• forming a conductive film over the thin film stack;
• forming a second etching mask over the conductive film;
• etching the conductive film to form a source electrode and a drain electrode;
• removing the second etching mask;
• and
• performing a first etching and a second etching on the thin film stack in a portion which does not overlap with the source electrode and the drain electrode to expose the crystalline semiconductor film in the portion which does not overlap with the source electrode and the drain electrode,
• wherein the first etching is performed using a first gas including a CF4 gas, and
• wherein the second etching is performed using a second gas including an HBr gas, a CF4 gas, and an oxygen gas.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film over the gate electrode;
• forming a crystalline semiconductor film over the gate insulating film;
• forming an amorphous semiconductor film over the crystalline semiconductor film;
• forming an impurity semiconductor film over the amorphous semiconductor film;
• forming a first etching mask over the impurity semiconductor film;
• etching a portion of the crystalline semiconductor film, the amorphous semiconductor film and the impurity semiconductor film which does not overlap with the first etching mask to form a thin film stack;
• removing the first etching mask;
• forming a conductive film over the thin film stack;
• forming a second etching mask over the conductive film;
• etching the conductive film to form a source electrode and a drain electrode;
• performing a first etching and a second etching on the thin film stack in a portion which does not overlap with the source electrode and the drain electrode to expose the crystalline semiconductor film in the portion which does not overlap with the source electrode and the drain electrode;
• and
• removing the second etching mask,
• wherein the first etching is performed using a first gas including a CF4 gas, and
• wherein the second etching is performed using a second gas including an HBr gas, a CF4 gas, and an oxygen gas.