Abstract
Amorphous carbon hard mask (ACHM) films are widely used as etching hard masks in 3D-NAND flash memory, which has put forward higher requirements in the film deposition rate, film transparency, uniformity, and selective etching. In this work, the ACHM film processing is engineered and optimized by comparatively studying acetylene (C2H2) and propylene (C3H6) as carbon sources at the different temperatures of 300 °C, 350 °C and 400 °C. By increasing the deposition temperature, the deposition rate, non-uniformity, and dry etch rate of ACHM are improved at the penalty of a slightly increased extinction coefficient of the film, due to lower incorporation of hydrocarbon reactants absorbed into film at higher temperatures. However, the Fourier transformation infrared (FTIR) spectrum intensity is decreased with the increase of the deposition temperature. The lower dry etch rate of ACHM is achieved by using C3H6 as a carbon source deposited at 400 °C. The best dry etch selective ratio values are also achieved with 10.9 and 9.5 for SiO2 and SiN, respectively. These experimental results can be very promising in the advancement of etching process in 3D-NAND applications.
Highlights
The exponential growth of mobile electronic devices like smartphones and fitness trackers has urged great demands for high performance and high density memory
For 3D-NAND, one of the key challenges is the requirement of a hard mask (HM) with better transparency and a higher etch selective ratio in lithograph and dry etch process due to a high aspect ratio pattern (HARP) [4,5,6]
amorphous carbon hard masks (ACHM) can be deposited by plasma-enhanced chemical vapor deposition (PECVD) with various carbon sources, such as methane (CH4), acetylene (C2H2), propylene (C3H6) and 1-hexene (C6H12) [17,18,19]
Summary
The exponential growth of mobile electronic devices like smartphones and fitness trackers has urged great demands for high performance and high density memory. For 3D-NAND, one of the key challenges is the requirement of a hard mask (HM) with better transparency and a higher etch selective ratio in lithograph and dry etch process due to a high aspect ratio pattern (HARP) [4,5,6]. Amorphous carbon hard masks (ACHM) have been used in semiconductor device fabrication, replacing the conventional SiO2 or Si3N4 HM due to its robust film properties such as high transparency, high etch selectivity, high durability for plasma Asher and easy elimination by oxygen (O2) plasma [10,11,12]. ACHM is characterized by an intermediate H content to amorphous carbon with sp2-bonded clusters, interconnected by a random network of sp3-bonded atomic sites. An experimental study comparing the film deposition, dry etch characteristics and approaches for higher selective ratios by using different precursors have been rarely reported
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