Method for manufacturing semiconductor device

A method of manufacturing a liquid crystal display comprising steps of:

• forming a gate electrode over a substrate having an insulating surface;
• forming a gate insulating film over the gate electrode;
• forming an oxide semiconductor layer containing In, Ga, and Zn over the gate insulating film;
• performing a first heat treatment on the oxide semiconductor layer in a first atmosphere;
• cooling the oxide semiconductor layer in a second atmosphere after the first heat treatment;
• forming a source electrode and a drain electrode over the oxide semiconductor layer after the step of cooling the oxide semiconductor layer;
• forming an oxide insulating layer over the source electrode, the drain electrode and the oxide semiconductor layer;
• performing a second heat treatment after forming the oxide insulating layer;
• and
• forming a pixel electrode after the second heat treatment,
• wherein the oxide insulating layer is in contact with the oxide semiconductor layer,
• wherein the pixel electrode is electrically connected to the source electrode or the drain electrode, and
• wherein in each of the first atmosphere and the second atmosphere a concentration of moisture or a concentration of hydrogen is low.

A method of manufacturing a liquid crystal display comprising steps of:

• forming a gate electrode over a substrate having an insulating surface;
• forming a gate insulating film over the gate electrode;
• forming an oxide semiconductor layer containing In, Ga, and Zn over the gate insulating film;
• performing a first heat treatment on the oxide semiconductor layer in a first atmosphere;
• cooling the oxide semiconductor layer in a second atmosphere after the first heat treatment;
• forming a source electrode and a drain electrode over the oxide semiconductor layer after the step of cooling the oxide semiconductor layer;
• forming an oxide insulating layer over the source electrode, the drain electrode and the oxide semiconductor layer;
• performing a second heat treatment after forming the oxide insulating layer;
• and
• forming a pixel electrode after the second heat treatment,
• wherein the oxide insulating layer is in contact with the oxide semiconductor layer,
• wherein the pixel electrode is electrically connected to the source electrode or the drain electrode, and
• wherein moisture or hydrogen is removed from each of the first atmosphere and the second atmosphere.

A method of manufacturing a liquid crystal display comprising steps of:

• forming a gate electrode over a substrate having an insulating surface;
• forming a gate insulating film over the gate electrode;
• forming an oxide semiconductor layer containing In, Ga, and Zn over the gate insulating film;
• performing a first heat treatment on the oxide semiconductor layer;
• cooling the oxide semiconductor layer after the first heat treatment;
• forming a source electrode and a drain electrode over the oxide semiconductor layer after the step of cooling the oxide semiconductor layer;
• forming an oxide insulating layer over the source electrode, the drain electrode and the oxide semiconductor layer;
• performing a second heat treatment after forming the oxide insulating layer;
• and
• forming a pixel electrode after the second heat treatment,
• wherein the oxide insulating layer is in contact with the oxide semiconductor layer,
• wherein the pixel electrode is electrically connected to the source electrode or the drain electrode, and
• wherein the first heating and the cooling are performed in an atmosphere in which a concentration of moisture or a concentration of hydrogen is reduced by an apparatus for removing moisture or hydrogen.

A method of manufacturing a liquid crystal display comprising steps of:

• forming a gate electrode over a substrate having an insulating surface;
• forming a gate insulating film over the gate electrode;
• forming an oxide semiconductor layer containing In, Ga, and Zn over the gate insulating film;
• performing a first heat treatment on the oxide semiconductor layer;
• cooling the oxide semiconductor layer after the first heat treatment;
• forming a source electrode and a drain electrode over the oxide semiconductor layer after the step of cooling the oxide semiconductor layer;
• forming an oxide insulating layer over the source electrode, the drain electrode and the oxide semiconductor layer;
• performing a second heat treatment after forming the oxide insulating layer;
• and
• forming a pixel electrode after the second heat treatment,
• wherein the oxide insulating layer is in contact with the oxide semiconductor layer,
• wherein the pixel electrode is electrically connected to the source electrode or the drain electrode, and
• wherein the first heating and the cooling are performed in an atmosphere from which moisture or hydrogen has been removed by an apparatus for removing moisture or hydrogen.