Semiconductor device and method for manufacturing semiconductor device
First Claim
1. A method for manufacturing a semiconductor device, the method comprising the steps of:
- providing a substrate having an electrically insulating top surface;
forming a first oxide semiconductor film over the substrate in a first atmosphere;
forming a second oxide semiconductor film on and in contact with the first oxide semiconductor film in a second atmosphere having a higher concentration in nitrogen than the first atmosphere;
forming a third oxide semiconductor film on and in contact with the second oxide semiconductor film;
performing heat treatment to the first oxide semiconductor film and the second oxide semiconductor film so that the first oxide semiconductor film is crystallized in a first crystal structure and the second oxide semiconductor film is crystallized in a second crystal structure different from the first crystal structure,wherein a concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the first oxide semiconductor film.
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Accused Products
Abstract
A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.
235 Citations
26 Claims
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1. A method for manufacturing a semiconductor device, the method comprising the steps of:
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providing a substrate having an electrically insulating top surface; forming a first oxide semiconductor film over the substrate in a first atmosphere; forming a second oxide semiconductor film on and in contact with the first oxide semiconductor film in a second atmosphere having a higher concentration in nitrogen than the first atmosphere; forming a third oxide semiconductor film on and in contact with the second oxide semiconductor film; performing heat treatment to the first oxide semiconductor film and the second oxide semiconductor film so that the first oxide semiconductor film is crystallized in a first crystal structure and the second oxide semiconductor film is crystallized in a second crystal structure different from the first crystal structure, wherein a concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the first oxide semiconductor film. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for manufacturing a semiconductor device, the method comprising the steps of:
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providing a substrate having an electrically insulating top surface; forming a first oxide semiconductor film over the substrate in a first atmosphere; forming a second oxide semiconductor film on and in contact with the first oxide semiconductor film in a second atmosphere having a higher concentration in nitrogen than the first atmosphere; performing heat treatment to the first oxide semiconductor film and the second oxide semiconductor film so that the first oxide semiconductor film is crystallized in a first crystal structure and the second oxide semiconductor film is crystallized in a second crystal structure different from the first crystal structure, forming a third oxide semiconductor film on and in contact with the second oxide semiconductor film; and performing an additional heat treatment on the third oxide semiconductor film so that the third oxide semiconductor film is crystallized in a third crystal structure, wherein a concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the first oxide semiconductor film, and wherein the concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the third oxide semiconductor film. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A semiconductor device comprising:
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a first insulating film; a second insulating film overlapping with the first insulating film; a stack of semiconductor films interposed between the first insulating film and the second insulating film, the stack of semiconductor films comprising; a first oxide semiconductor film; a second oxide semiconductor film on and in contact with the first oxide semiconductor film; and a third oxide semiconductor film on and in contact with the second oxide semiconductor film and interposed between the second oxide semiconductor film and the second insulating film; and an electrically conducting film overlapping with the stack of semiconductor films with the second insulating film interposed therebetween, wherein a concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the first oxide semiconductor film. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A semiconductor device comprising:
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a first insulating film; a second insulating film overlapping with the first insulating film; a stack of semiconductor films interposed between the first insulating film and the second insulating film, the stack of semiconductor films comprising; a first oxide semiconductor film; a second oxide semiconductor film in contact with the first oxide semiconductor film and interposed between the first oxide semiconductor film and the second insulating film; and a third oxide semiconductor film interposed between the second oxide semiconductor film and the second insulating film, and an electrically conducting film overlapping with the stack of semiconductor films with the second insulating film interposed therebetween, wherein a concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the first oxide semiconductor film, and wherein the concentration in nitrogen of the second oxide semiconductor film is higher than a concentration in nitrogen of the third oxide semiconductor film. - View Dependent Claims (22, 23, 24, 25, 26)
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Specification