Method of making a semiconductor device using treated photoresist
View Patent ↗A semiconductor device is made by patterning a conductive layer for forming gates of transistors. The process for forming the gates has a step of patterning photoresist that overlies the conductive layer. The patterned photoresist is trimmed so that its width is reduced. Fluorine, preferably F 2 , is applied to the trimmed photoresist to increase its hardness and its selectivity to the conductive layer. Using the trimmed and fluorinated photoresist as a mask, the conductive layer is etched to form conductive features useful as gates. Transistors are formed in which the conductive pillars are gates. Other halogens, especially chlorine, may be substituted for the fluorine.
1. A method for forming a semiconductor device comprising:
providing a substrate;
providing a layer to be patterned overlying the substrate;
providing a patterned photoresist layer overlying the layer to be patterned, the patterned photoresist layer having a minimum dimension;
trimming the patterned photoresist layer;
applying molecular fluorine gas to the patterned photoresist layer to change a property of the photoresist layer to be more resistant to a subsequent etch processing; and
transferring the pattern of the trimmed patterned photoresist layer into the layer to be patterned.
2. The method of claim 1 , wherein the layer to be patterned includes a stack of layers.
3. The method of claim 2 , wherein the stack of layers including a sacrificial layer overlying an underlying layer to be patterned.
4. The method of claim 1 , wherein trimming includes reducing the minimum dimension via at least one of mechanical and chemical processing.
5. The method of claim 4 , wherein mechanical processing includes at least one of reactive ionic etching (RIE) and ionic bombardment etching.
6. The method of claim 4 , wherein chemical processing includes reacting with at least oxygen.
7. The method of claim 4 , wherein the minimum dimension is reduced by up to 80 percent of the minimum dimension.
8. The method of claim 4 , wherein the minimum dimension is on the order of 100 nanometers and wherein by trimming, the minimum dimension is reduced to within a range of on the order of 20–80 nanometers.
9. The method of claim 1 , wherein the property includes at least one of a chemical and a physical nature.
10. The method of claim 1 , wherein the transferring the pattern includes at least a pattern transfer etch processing.
11. The method of claim 1 , wherein the patterned photoresist layer is characterized by a first amount of high frequency line edge roughness, and wherein the applying molecular fluorine gas promotes at least one of i) a reduction in high frequency line edge roughness and ii) a resistance to additional high frequency line edge roughness.
12. The method of claim 1 , wherein the trimming and the applying molecular fluorine gas are performed in a same tool.
13. The method of claim 1 , wherein the layer to be patterned includes at least one of a conductive material, a semiconductive material, and an insulating material.
14. The method of claim 1 , wherein the trimmed patterned photoresist layer includes a portion for forming a control electrode of a transistor.
15. A method for forming a semiconductor device, comprising:
providing a semiconductor substrate;
applying a photoresist layer over the substrate;
patterning the photoresist layer to form a patterned photoresist layer;
applying molecular fluorine to the patterned photoresist layer; and
after applying the molecular fluorine, using the patterned photoresist to provide a pattern corresponding to the patterned photoresist under the patterned photoresist.
16. The method of claim 15 , forming, prior to applying the photoresist, a layer over the semiconductor substrate, and wherein the pattern is formed in the layer.
17. The method of claim 16 , wherein the applying the molecular fluorine alters a property of the patterned photoresist.
18. The method of claim 17 , wherein the altered property is stiffness.
19. The method of claim 17 , wherein the altered property is resistance to being etched.