US 12,259,654 B2
Method for manufacturing semiconductor device
Tadashi Watanabe, Yokohama (JP); and Takahide Hirasaki, Osaka (JP)
Assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD., Osaka (JP)
Filed by SUMITOMO ELECTRIC INDUSTRIES, LTD., Osaka (JP)
Filed on Jan. 12, 2021, as Appl. No. 17/147,181.
Claims priority of application No. 2020-003728 (JP), filed on Jan. 14, 2020.
Prior Publication US 2021/0216014 A1, Jul. 15, 2021
Int. Cl. G03F 7/11 (2006.01); G03F 7/09 (2006.01); H01L 21/027 (2006.01); H01L 29/20 (2006.01); H01L 29/66 (2006.01); H01L 29/778 (2006.01)
CPC G03F 7/11 (2013.01) [G03F 7/094 (2013.01); H01L 21/0274 (2013.01); H01L 29/2003 (2013.01); H01L 29/66462 (2013.01); H01L 29/7786 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A method for manufacturing a semiconductor device comprising steps of:
forming a first photoresist film on a semiconductor substrate, and forming a second photoresist film having a higher acidity than the first photoresist film on an upper surface of the first photoresist film;
forming a first opening for exposing a surface of the semiconductor substrate by patterning the first photoresist film and the second photoresist film;
applying shrink material to an upper surface of the second photoresist film and inside of the first opening, the shrink material touching a first side surface of the first photoresist film and a second side surface of the second photoresist film within the first opening;
heat-treating the first photoresist film, the second photoresist film and the shrink material simultaneously so as to form a shrink film on the second side surface of the second photoresist film and on the upper surface of the second photoresist film, with the shrink material having a greater reaction with the second side surface and the upper surface of the second photoresist film than with the first side surface of the first photoresist film, the second photoresist film having an upper portion and a lower portion, the lower portion being located between the upper portion and the first photoresist film and having an acidity lower than an acidity of the upper portion and higher than an acidity of the first photoresist film; and
removing unreacted shrink material that does not react with the first photoresist film and the second photoresist film by washing with water so as to form a second opening in the shrink film from the first opening, and a third opening in the first photoresist film from the first opening, the second opening having an opening length on an upper surface of the second opening, the opening length being smaller than a minimum opening length in the third opening, and the second opening having a tapered shape in a cross-sectional view of the second photoresist film, wherein
the shrink material includes polyvinyl alcohol,
the first photoresist film and the second photoresist film include a novolac resin,
the first photoresist film and the second photoresist film further include ethyl lactate, and
a weight concentration of ethyl lactate in the second photoresist film is 5 times or more higher than that of ethyl lactate in the first photoresist film.