The present invention relates to a chemical mechanical polishing method and a method of manufacturing a semiconductor device.
In the manufacturing process of semiconductor devices, a resist film is used to form a desired structure. The resist film is required to have a uniform thickness over the entire wafer. For example, a desired structure is obtained by forming a trench in a semiconductor substrate or a hole in an insulating film, applying a photoresist to form a resist film, and recessing or removing the resist film.
In this case, the resist film is required to have a uniform thickness over the entire wafer.
A variation in thickness of the resist film is increased during the subsequent recess step to cause the device shape to deteriorate. Moreover, a decrease in depth of focus or yield occurs.
In order to solve the problems caused by such a variation in thickness of the resist film, a method has been proposed in which the resist film is planarized by chemical mechanical polishing (CMP) after applying the resist (e.g. JP-A-2004-363191).
However, it is difficult to suppress dishing which occurs during planarization. Moreover, wafer in-plane uniformity is poor. When dishing in-plane uniformity is poor, the recess depth varies in the subsequent step. This makes it difficult to uniformly obtain a desired shape on the wafer surface, whereby a pattern dimensional variation occurs.
When polishing a resist film of which the hardness is increased by baking at a high temperature, inorganic particles such as silica or alumina are used as abrasive particles in order to ensure a practical process margin and productivity. In this case, since the inorganic particles tend to remain in the trench, the surface state deteriorates due to occurrence of scratches. Moreover, a problem occurs in which the residual particles serve as a mask during the recess step after CMP.