Pitch reduced patterns relative to photolithography features
Differently-sized features of an integrated circuit are formed by etching a substrate using a mask which is formed by combining two separately formed patterns. Pitch multiplication is used to form the relatively small features of the first pattern and conventional photolithography used to form the relatively large features of the second pattern. Pitch multiplication is accomplished by patterning a photoresist and then etching that pattern into an amorphous carbon layer. Sidewall spacers are then formed on the sidewalls of the amorphous carbon. The amorphous carbon is removed, leaving behind the sidewall spacers, which define the first mask pattern. A bottom anti-reflective coating (BARC) is then deposited around the spacers to form a planar surface and a photoresist layer is formed over the BARC. The photoresist is next patterned by conventional photolithography to form the second pattern, which is then is transferred to the BARC. The combined pattern made out by the first pattern and the second pattern is transferred to an underlying amorphous silicon layer and the pattern is subjected to a carbon strip to remove BARC and photoresist material. The combined pattern is then transferred to the silicon oxide layer and then to an amorphous carbon mask layer. The combined mask pattern, having features of difference sizes, is then etched into the underlying substrate through the amorphous carbon hard mask layer.
1. A method for semiconductor fabrication, comprising:
providing an amorphous carbon layer over a substrate;
providing a lower hard mask layer over the amorphous carbon layer;
providing an upper hard mask layer on the lower hard mask layer, the upper hard mask layer formed of a different material than the lower hard mask layer;
providing a mask with a mask pattern on the upper hard mask layer;
transferring the mask pattern to the upper hard mask layer;
transferring a pattern in the upper hard mask layer to the lower hard mask layer in a next pattern transfer step immediately following transferring the mask pattern to the upper hard mask layer;
transferring a pattern in the lower hard mask layer to the amorphous carbon layer; and
transferring a pattern in the amorphous carbon layer into the substrate.
2. The method of claim 1 , wherein features in the mask disposed on the upper hard mask layer have a pitch of about 100 nm or less.
3. The method of claim 1 , wherein transferring the pattern in the lower hard mask layer to the amorphous carbon layer comprises performing a plasma etch comprising SO 2 .
4. The method of claim 1 , wherein the amorphous carbon is transparent carbon.
5. The method of claim 1 , wherein transferring the pattern to the upper hard mask layer; transferring the pattern in the upper hard mask layer to the lower hard mask layer; transferring the pattern in the lower hard mask layer to the amorphous carbon layer; and transferring the pattern in the amorphous carbon layer to the substrate each comprise performing an anisotropic etch.