Forming method of N-channel metal oxide semiconductor (NMOS) transistor

Abstract

The invention discloses a forming method of an N-channel metal oxide semiconductor (NMOS) transistor, which comprises the following steps of: providing a semiconductor substrate which is divided into an isolation region and an active region; forming a doped well in the semiconductor substrate of the active region; forming a gate dielectric layer and a polycrystalline silicon gate on the semiconductor substrate of the active region in turn, wherein the gate dielectric layer and the polycrystalline silicon gate form a gate structure; re-oxidizing the gate structure; injecting ions into the semiconductor substrates on two sides of the gate by taking the gate structure as a mask to form a source / drain extension region; forming side walls on two sides of the gate structure, and then forming a Vt injection region in the semiconductor substrate; and forming source / drain electrodes in the semiconductor substrates on two sides of the gate structure and the side walls. The forming method ensures that ions of the Vt injection region of a channel region positioned below the gate are uniformly distributed to prevent a reverse short channel effect (RSCE).

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for forming an NMOS transistor. Background technique [0002] As the semiconductor industry develops towards smaller and faster devices, the feature lateral dimensions and depths of semiconductor devices are gradually reduced, requiring source / drain and source / drain extensions to become shallower accordingly, The current state of the art requires the depth of the source / drain junction of semiconductor devices to be less than 1000 angstroms, and may eventually require the junction depth to be on the order of 200 angstroms or less. Currently, the source / drain junction is almost always formed by doping by ion implantation. As the size of electronic components shrinks, how to manufacture the source and drain of metal-oxide-semiconductor (MOS) transistors with nanometer process technology is the development direction of ion implantation technology at present and in th...

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Problems solved by technology

[0008] When forming a MOS transistor in the prior art, during the re-oxidation process of the gate structure, oxygen ions will react with the silicon in the semiconductor substrate, and the silicon atoms will be squeezed into the channel region to form interstitial atoms, so that the boron in the Vt implantation region Ions diffuse by combining with silicon interstitial atoms, and silicon interstitial atoms tend to recombine at the interface between silicon and silicon dioxide, which increases the concentration of boron ions at the surface of the channel region at the edge of the gate, affecting the distribution of ions in the Vt implantation region Inhomogeneous; as the channel length shrinks, the high concentration of boron ions at the edge of the gate will cause the threshold voltage of the channel region to rise rapidly, resulting in serious reverse short channel effect (RSCE), and the threshold voltage caused by RSCE is distributed with the gate length The unevenness of the device is easy to cause a large drift of device characteristics due to process fluctuations

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