Plasma Etching for Sub-45-nm TaN Metal Gates on High-k Dielectrics |
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Authors: | Bliznetsov V.N. Bera L.K. Haw Yun Soo Balasubramanian N. Kumar R. Guo-Qiang Lo Won Jong Yoo Chih Hung Tung Linn L. |
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Affiliation: | Inst. of Microelectron., Singapore; |
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Abstract: | Etching of TaN gates on high-k dielectrics (HfO2 or HfAlO) is investigated using HBr/Cl2 chemistry in a decoupled plasma source (DPS). The patterning sequence includes 248-nm lithography, plasma photoresist trimming, etching of a SiN-SiO2 hard mask, and photoresist stripping, followed by TaN etching. TaN etching is studied by design of experiment (DOE) with four variables using a linear model with interactions. It is found that at a fixed substrate temperature and wafer chuck power, etch critical dimensions (CD) gain decreases with decreasing HBr/Cl2 flow rate ratio and pressure and with increasing source power and total gas flow rate. Based on these DOE findings, subsequent optimization is performed and a three-step etching process is developed; a main feature of the process is progressively increasing HBr/Cl2 flow rate ratio. The optimized process provides etch CD gain within 2 nm and gate profile close to vertical and reliable etch-stop on high-k dielectric. This process is successfully applied to the fabrication of the 40-nm HfAlO/TaN gate stack p-MOSFETs with good electrical parameters |
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