Method of forming an etching mask pattern from developed negative and positive photoresist layers
The present invention relates to a method of forming an etching mask pattern from developed negative and positive photoresist layers. According to the present invention, a negative photoresist layer is formed over a substrate. Some regions of the negative photoresist layer are exposed, thereby generating hydrogen ions within the exposed negative photoresist regions. The negative photoresist layer is developed so that the exposed negative photoresist regions remain. A positive photoresist layer is formed over the substrate including the remaining negative photoresist regions. The substrate is baked so that hydrogen ions within the remaining negative photoresist regions are diffused into the positive photoresist layer at boundary portions adjacent to the remaining negative photoresist regions. The positive photoresist layer is developed to remove the positive photoresist portions into which the hydrogen ions are diffused.
1. A method of forming an etching mask pattern from developed negative and positive photoresist layers, comprising:
forming a negative photoresist layer over a substrate;
exposing some regions of the negative photoresist layer, thereby generating hydrogen ions within the exposed negative photoresist regions;
developing the negative photoresist layer so that the exposed negative photoresist regions remain;
forming a positive photoresist layer over the substrate including the remaining negative photoresist regions;
baking the substrate so that hydrogen gas ions within the remaining negative photoresist regions are diffused into the positive photoresist layer at boundary portions adjacent to the remaining negative photoresist regions; and
developing the positive photoresist layer to remove the positive photoresist portions into which the hydrogen ions are diffused.
2. The method of claim 1 , further comprising forming a Bottom Anti-Reflective Coating (BARC) layer before the formation of the negative photoresist layer.
3. The method of claim 1 , wherein each of the negative photoresist layer and the positive photoresist layer is formed using a chemically amplified photoresist.
4. The method of claim 1 , wherein a sum of a width of one remaining negative photoresist region and a width of a first space adjacent to the one remaining negative photoresist region defines a first pattern pitch, which is twice a resolution of an exposure equipment.
5. The method of claim 1 , wherein the positive photoresist layer is formed so that a thickness on a top of the remaining negative photoresist regions is thinner than a penetration thickness of the hydrogen ions, which will be diffused from the remaining negative photoresist regions into the surrounding positive photoresist layer adjacent to each side portion of the remaining negative photoresist regions, through baking.
6. The method of claim 1 , wherein the positive photoresist layer is formed so that a penetration thickness of the hydrogen ions diffused into a lateral portion of the positive photoresist layer is thicker than a penetration thickness of the hydrogen ions diffused on a top of the remaining negative photoresist region.
7. The method of claim 1 , wherein the etching mask pattern has a second pattern pitch, which becomes a target distance by removing the positive photoresist portions including the hydrogen ions diffused from each side portion of the remaining negative photoresist region.
8. The method of claim 1 , wherein the etching mask pattern includes the remaining negative photoresist region and remaining positive photoresist region, which are spaced apart from each other by a second space and are alternately formed.
9. The method of claim 8 , wherein the etching mask pattern is formed such that a sum of either a width of one of the remaining negative photoresist regions or a width of one of the remaining positive photoresist regions and a width of the second space has a same second pattern pitch as a resolution of an exposure equipment.