Method of manufacturing a semiconductor device with a front-end insulating layer interposed between a semiconductor layer and an insulating substrate
View Patent ↗A semiconductor device in which a semiconductor layer is formed on an insulating substrate with a front-end insulating layer interposed between the semiconductor layer and the insulating substrate is provided which is capable of preventing action of an impurity contained in the insulating substrate on the semiconductor layer and of improving reliability of the semiconductor device. In a TFT (Thin Film Transistor), boron is made to be contained in a region located about 100 nm or less apart from a surface of the insulating substrate so that boron concentration decreases at an average rate being about 1/1000-fold per 1 nm from the surface of the insulating substrate toward the semiconductor layer.
1. A method for manufacturing a semiconductor device in which a semiconductor layer is formed on an insulating substrate with a front-end insulating layer being interposed between said semiconductor layer and said insulating substrate, said front-end insulating layer having a lower layer insulating film and an upper layer insulating film, said method comprising:
a process of forming said front-end insulating layer on said insulating substrate in which impurity concentration decreases at an average rate being about 1/1000-fold or less per 1 nm from a surface of said insulating substrate toward said semiconductor layer.
2. The method for manufacturing the semiconductor device according to claim 1 , further comprising a process of forming said region of said front-end insulating layer in which said impurity concentration decreases at the average rate being about 1/1000-fold or less per 1 nm from the surface of said insulating 5 substrate toward said semiconductor layer in a region located about 100 nm or less apart from a surface of said insulating substrate.
3. The method for manufacturing the semiconductor device according to claim 2 , still further comprising a process of controlling so that said impurity concentration in said region of said front-end insulating layer located about 100 nm or more apart from said surface of said insulating substrate is about 10 19 (atom/cm 3 ) or less.
4. The method for manufacturing the semiconductor device according to claim 1 , still further comprising a process of forming said region of said front-end insulating layer in which said impurity concentration decreases at the average rate being about 1/1000-fold or less per 1 nm from the surface of said insulating substrate toward said semiconductor layer at least under a gate electrode.
5. The method for manufacturing the semiconductor device according to claim 1 , still further comprising a process of making boron, aluminum, a substance containing boron, or substance containing aluminum be contained as said impurity.
6. The method for manufacturing the semiconductor device according to claim 1 , still further comprising a process of making boron or a substance containing boron be contained in said front-end insulating layer so that boron concentration decreases at an average rate being about 1/100000-fold to about 1/1000-fold per 1 nm.
7. The method for manufacturing the semiconductor device according to claim 1 , still further comprising a process of making aluminum or a substance containing aluminum be contained in said front-end insulating layer so that boron concentration decreases at an average rate being about 1/100000-fold to about 1/1000-fold per 1 nm.
8. The method for manufacturing the semiconductor device according to claim 5 , wherein boron concentration or aluminum concentration is calculated by secondary ion mass spectroscopy.
9. The method for manufacturing the semiconductor device according to claim 1 , wherein said lower layer insulating film is made of a silicon nitride film, and said upper layer insulating film is made of a silicon oxide film.