Method for manufacturing semiconductor device
First Claim
1. A method for manufacturing a semiconductor device comprising the steps of:
- forming a first oxide semiconductor film over an insulating layer;
forming a second oxide semiconductor film over the first oxide semiconductor film;
performing a first heat treatment on the first oxide semiconductor film and the second oxide semiconductor film and then cooling the first oxide semiconductor film and the second oxide semiconductor film in an atmosphere containing oxygen;
etching the first oxide semiconductor film and the second oxide semiconductor film after the cooling step to form a first oxide semiconductor layer from the first oxide semiconductor film and a second oxide semiconductor layer from the second oxide semiconductor film;
forming a conductive film over the first oxide semiconductor layer and the second oxide semiconductor layer;
etching the second oxide semiconductor layer and the conductive film to form a source region, a drain region, a source electrode layer, and a drain electrode layer; and
forming an oxide insulating film in contact with part of the first oxide semiconductor layer.
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Abstract
It is an object to provide a highly reliable semiconductor device which includes a thin film transistor having stable electric characteristics. It is another object to manufacture a highly reliable semiconductor device at lower cost with high productivity. In a method for manufacturing a semiconductor device which includes a thin film transistor where a semiconductor layer having a channel formation region, a source region, and a drain region are formed using an oxide semiconductor layer, heat treatment (heat treatment for dehydration or dehydrogenation) is performed so as to improve the purity of the oxide semiconductor layer and reduce impurities such as moisture. Moreover, the oxide semiconductor layer subjected to the heat treatment is slowly cooled under an oxygen atmosphere.
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Citations
30 Claims
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1. A method for manufacturing a semiconductor device comprising the steps of:
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forming a first oxide semiconductor film over an insulating layer; forming a second oxide semiconductor film over the first oxide semiconductor film; performing a first heat treatment on the first oxide semiconductor film and the second oxide semiconductor film and then cooling the first oxide semiconductor film and the second oxide semiconductor film in an atmosphere containing oxygen; etching the first oxide semiconductor film and the second oxide semiconductor film after the cooling step to form a first oxide semiconductor layer from the first oxide semiconductor film and a second oxide semiconductor layer from the second oxide semiconductor film; forming a conductive film over the first oxide semiconductor layer and the second oxide semiconductor layer; etching the second oxide semiconductor layer and the conductive film to form a source region, a drain region, a source electrode layer, and a drain electrode layer; and forming an oxide insulating film in contact with part of the first oxide semiconductor layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for manufacturing a semiconductor device comprising the steps of:
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forming a first oxide semiconductor film over an insulating layer; forming a second oxide semiconductor film over the first oxide semiconductor film; performing a first heat treatment on the first oxide semiconductor film and then cooling the first oxide semiconductor film in an atmosphere containing oxygen; etching the first oxide semiconductor film and the second oxide semiconductor film after the cooling step to form a first oxide semiconductor layer from the first oxide semiconductor film and a second oxide semiconductor layer from the second oxide semiconductor film; forming a conductive film over the first oxide semiconductor layer and the second oxide semiconductor layer; etching the second oxide semiconductor layer and the conductive film to form a source region, a drain region, a source electrode layer, and a drain electrode layer; and forming an oxide insulating film in contact with part of the first oxide semiconductor layer. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for manufacturing a semiconductor device comprising the steps of:
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forming a first oxide semiconductor film over an insulating layer; forming a second oxide semiconductor film over the first oxide semiconductor film; performing a first heat treatment on the first oxide semiconductor film and the second oxide semiconductor film and then cooling the first oxide semiconductor film and the second oxide semiconductor film in an atmosphere containing oxygen; etching the first oxide semiconductor film and the second oxide semiconductor film after the cooling step to form a first oxide semiconductor layer from the first oxide semiconductor film and a second oxide semiconductor layer from the second oxide semiconductor film; forming a conductive film over the first oxide semiconductor layer and the second oxide semiconductor layer; etching the second oxide semiconductor layer and the conductive film to form a source region, a drain region, a source electrode layer, and a drain electrode layer; and forming an oxide insulating film in contact with part of the first oxide semiconductor layer, wherein the first oxide semiconductor layer includes crystal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification