| 摘要 |
In fabrication processes of semiconductor integrated circuit devices, a technique for improving the carrier mobility has been frequently employed. This technique utilizes strain caused by the stress typically of a silicon nitride film. With this, a batchwise wet processing with hot phosphoric acid should be performed so as to highly selectively remove the silicon nitride film over a complicated device structure on a front side of a wafer. This processing removes also a silicon nitride film on the back side of the wafer, and after a series of strain-imparting processes, a polysilicon member is exposed from the back side surface of the wafer. However, common techniques for cleaning typically of back sides of wafers may not sufficiently effectively clean the back side containing a polysilicon as a main component, because these techniques are designed to be adopted to a back side containing, for example, a silicon nitride film, but the polysilicon and the silicon nitride film differ from each other in properties. To void the problem, a wet cleaning process is performed before a lithography process. The wet cleaning process includes two steps, in which FPM cleaning and SPM cleaning are performed in this order.
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