PMOS transistor forming method

Abstract

The invention discloses a PMOS transistor forming method. The method comprises the steps: adding a fifth subphase that the flow gradually decreases between a first subphase that a germanium source gas flow gradually increases and a second subphase that the flow is table for a phase that silicon germanium seed crystal is formed in a sigma groove of a source-drain region, wherein the initial flow of germanium source gas at the fifth subphase is equal to the tail flow of the first subphase; and/or adding a sixth subphase that the flow gradually decreases between a third subphase that a gas flow gradually increases and a fourth subphase that the flow is table for a phase that a bulk material is formed, wherein the initial flow of germanium source gas at the sixth subphase is equal to the tail flow of the third subphase. The method can the flow abrupt changes at the joint of the first and second subphases and/or the joint of the third and fourth subphases from causing the abrupt increase of the content of germanium in a formed silicon germanium material, avoids the mismatching of the silicon germanium material crystal lattices, and avoids current leakage caused by that carriers of the source-drain regions enter a trench region because of the recessing of a side wall of the sigma groove.

Description

Technical field [0001] The present invention relates to the technical field of semiconductor manufacturing, in particular to a method for forming a PMOS transistor. Background technique [0002] In the existing semiconductor device manufacturing process, since stress can change the energy gap and carrier mobility of silicon materials, improving the performance of MOS transistors through stress has become an increasingly common method. Specifically, a sigma-shaped groove is formed in the source / drain region of the transistor, and compressive stress or tensile stress material is filled in it, and the tip of the sigma-shaped groove is used to apply compressive or tensile stress to the channel, thereby improving the groove The mobility of carriers in the channel (electrons in NMOS transistors, holes in PMOS transistors). [0003] In the actual process, it is found that the PMOS transistors manufactured above often have large leakage currents, and the performance of multiple PMOS trans...

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Problems solved by technology

[0003] In the actual process, it is found that the PMOS transistors manufactured above often have large leakage currents, and the performance of multiple PMOS transistors manufactured in the same batch is unstable, such as saturation leakage current drift and other problems.

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