Method of manufacturing semiconductor device
A method of manufacturing a semiconductor device has forming a first nitride layer over a substrate, forming a first oxide layer on the first nitride layer, forming a second nitride layer on the first oxide layer, forming a photoresist layer over the second nitride layer, forming a opening in the photoresist layer, etching the second nitride layer using the photoresist layer as a mask such that the opening is reached to the first oxide layer, etching the first oxide layer using the second nitride layer as a mask such that the opening is reached to the first nitride layer, etching the first oxide layer such that bottom zone of the opening is increased in diameter, and etching the first nitride layer using the first oxide layer as a mask such that the opening is reached to the substrate thereby to form contact hole reaching to the substrate.
1. A method of manufacturing a semiconductor device, comprising:
forming a first nitride layer over a substrate;
forming a first oxide layer on the first nitride layer;
forming a second nitride layer on the first oxide layer;
forming a photoresist layer over the second nitride layer;
forming an opening in the photoresist layer;
etching the second nitride layer by using the photoresist layer as a mask such that the opening reaches the first oxide layer;
etching the first oxide layer by using the second nitride layer as a mask such that the opening reaches the first nitride layer;
etching the first oxide layer such that a bottom zone of the opening is increased in diameter; and
etching the first nitride layer by using the first oxide layer as a mask such that the opening reaches the substrate thereby to form a contact hole reaching to the substrate;
wherein a content rate of CF polymer in an etching gas used in the etching of the first oxide layer such that the bottom zone of the opening is increased in diameter is greater than a content rate of CF polymer in an etching gas used in the etching of the first oxide layer by using the second nitride layer as a mask such that the opening is reached to the first nitride layer.
2. The method according in claim 1 , wherein the forming the first nitride layer over the substrate is performed by forming a transistor on the substrate, and forming the first nitride layer over the transistor and the substrate, and wherein the etching the first nitride layer is performed such that the contact hole reach to a source and/or drain electrode of the transistor.
3. The method according to claim 1 , wherein the etching the first oxide layer such that bottom zone of the opening is increased in diameter etches off the bottom zone of the opening in diameter without varying the diameter of zone of the opening that are the same diameter as the upper surface of the second nitride layer.
4. The method according to claim 1 , further comprising forming a second oxide layer on the second nitride layer after the forming the second nitride layer on the first oxide layer and before the forming the photoresist layer over the second nitride layer, and
wherein the etching the second nitride layer is performed by etching the second oxide layer and the second nitride layer using the photoresist layer as a mask.
5. The method according to claim 1 , wherein a diameter of a bottom zone of the opening is controlled in the etching the first oxide layer such that bottom zone of the opening is increased in diameter on the basis of etching amount of the first oxide layer.
6. The method according to claim 1 , wherein the selectivity of the first oxide layer to the first nitride layer etched in the etching of the first oxide layer such that the bottom zone of the opening is increased in diameter is greater than the selectivity of the first oxide layer to the first nitride layer etched in the etching of the first oxide layer by using the second nitride layer as a mask such that the opening is reached to the first nitride layer.
7. The method according to claim 1 , wherein the etching the second nitride layer is performed by applying an etching gas including CF 4 , an etching gas including mixing gaseous CF 4 and CHF 3 , an etching gas including mixing gaseous CF 4 and CH 2 F 2 , or an etching gas including mixing gaseous CF 4 , CHF 3 , and CH 2 F 2 is applied to the etching the second nitride layer.
8. The method according to claim 1 , wherein the etching the second nitride layer is performed such that the opening is tapered toward the bottom zone of the opening.
9. The method according to claim 1 , wherein the first nitride layer is a first silicon nitride layer, the first oxide layer is a first silicon dioxide layer, and the second nitride layer is a second silicon nitride layer.
10. The method according to claim 1 , wherein the etching the first nitride layer is performed such that the second nitride layer is etched off while the etching the first nitride layer is performed to etch the first nitride layer.