Method for improving dielectric constant of gate oxide

Abstract

The invention discloses a method for improving the dielectric constant of a gate oxide and relates to the field of manufacturing process of a semiconductor MOS device and particularly relates to a method for improving the dielectric constant of the gate oxide. The method includes the following steps: providing a substrate; preparing a SiO2 gate oxide layer on the substrate; performing nitrogen injection on the SiO2 gate oxide layer so that part of oxygen atoms in the SiO2 are replaced by nitrogen atoms and thus an SiON gate oxide layer is formed; in an environment which is higher than 1000 DEG C and surrounded by a pure inert gas, performing nitrogen treatment on the SiON gate oxide layer so as to repair lattice damages and form stable Si-N bonds; and in an environment which is lower than 800 DEG C, performing oxidation treatment on the SiON gate oxide layer so as to repair an SiO2 / Si interface. Compared with a traditional high-temperature nitrogen treatment process, the SiON gate oxide layer prepared through the method is stable in nitrogen content and the nitrogen content of the gate oxide can be improved effectively by about 30% so that the prepared gate oxide has a higher dielectric constant and thus an objective of precise cut-out on the dielectric constant of a SiON gate dielectric is realized.

Description

technical field [0001] The invention relates to the field of manufacturing technology for semiconductor MOS devices, in particular to a method for increasing the dielectric constant of gate oxide. Background technique [0002] The preparation process of the gate oxide layer is a key technology in the semiconductor manufacturing process, which directly affects and determines the electrical characteristics and reliability of the device. Since the semiconductor technology entered the 45nm era, the gate dielectric SiO 2 The thickness is already very thin (less than ), the tunneling mechanism in the gate leakage has played a dominant role. With SiO 2 With further reduction in thickness, the gate leakage current will also increase exponentially. gate dielectric thickness per reduction , the gate leakage current will increase by 10 times. On the other hand, gate, SiO 2 There is a concentration gradient of impurities between the gate dielectric and the silicon substrate. As...

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Problems solved by technology

At present, there are usually three main methods in the industry to realize SiO 2 Nitrogen doping in the gate dielectric to form SiON, but due to the high concentration of nitrogen atoms doped in the gate dielectric and mainly distributed on the upper surface of the gate dielectric, the temperature, gas atmosphere and The time interval must be strictly controlled to prevent the influence of the intrinsic oxide layer and organic adsorption on nitrogen doping; in addition, the high-temperature annealing process of PNA (Post Nitridation Anneal) can easily cause the volatilization of surface nitrogen atoms and make nitrogen atoms Gain energy and continue to diffuse, causing some nitrogen atoms to accumulate in SiO 2 / Si interface, thus negatively affecting the mobility of carriers in the channel

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