BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a polishing composition and a polishing method.

Description of the Related Art

In recent years, with multilayer-wiring on the surface of a semiconductor substrate, a so-called chemical mechanical polishing (CMP) art of polishing the semiconductor substrate for planarization has been used in manufacturing a device. The CMP is a method for planarizing the surface of a polishing object (object to be polished), such as a semiconductor substrate, using a polishing composition (slurry) containing abrasives, such as silica, alumina, and ceria, an anticorrosive, a surfactant, and the like. Examples of the polishing object (object to be polished) include silicon, polysilicon, a silicon oxide film (silicon oxide), silicon nitride, wiring lines containing a metal and the like, a plug, and the like.

For the polishing composition used in polishing a semiconductor substrate by the CMP, various proposals have been made so far.

For example, PTL 1 describes a polishing composition for improving the polishing characteristics to polysilicon, particularly improving level difference elimination efficiency. The polishing composition contains abrasives (colloidal silica) and an oxidant and has a pH of 6 or more. It is described that the polishing composition improves level difference elimination characteristics to a polishing object having a level difference because the oxidant applies a chemical action to chemically polish the surface of polysilicon which is a polishing object in the composition having a pH of 6 or more.

Moreover, PTL 1 describes a polishing composition containing 500 ppm of polyvinylpyrrolidone having a weight average molecular weight of 40,000 as an example of a water-soluble polymer which is an additive compounded in order to further improve the level difference elimination efficiency. The polishing composition has a pH of 9 and contains 0.1 mass % of hydrogen peroxide.

PTL 2 describes an additive for CMP abrasives containing an organic compound having an acetylene bond, a water-soluble vinyl polymer, and water, having a pH of 4 to 9, and capable of polishing an inorganic insulating film for semiconductors by being combined with a cerium oxide slurry for semiconductors. It is described that the compounding of the additive can improve the polishing uniformity of the entire surface of the wafer plane to improve the planarization characteristics of the entire surface of the wafer plane. Polyvinylpyrrolidone is not illustrated as the water-soluble vinyl polymer.

PTL 3 describes, as a polishing composition for the use of roughly polishing a silicon wafer, a polishing composition containing abrasives, a nitrogen containing water-soluble polymer (polyvinylpyrrolidone, content of 0.005 mass % or less) containing two kinds of the same structure different in weight average molecular weight (first nitrogen containing water-soluble polymer and second nitrogen containing water-soluble polymer), a basic compound, and water. Moreover, as the compounding ratio of the two kinds of the nitrogen containing water-soluble polymers, First nitrogen containing water-soluble polymer (weight average molecular weight of 300,000 or more):Second nitrogen containing water-soluble polymer (weight average molecular weight of less than 300,000)=5:1 to 1:20 is descried.

CITATION LIST

Patent Literature

PTL 1: JP 2015-86355 APTL 2: JP 2008-85058 APTL 3: WO 2019/116833

SUMMARY OF THE INVENTION

A step of manufacturing a semiconductor device includes polishing a polishing object having a polysilicon film (film containing a silicon material having a silicon-silicon bond) formed on a pattern containing a silicon nitride film (insulating film) by the CMP method to form circuit patterns containing the polysilicon film, for example. Examples of problems occurring in the polishing include the occurrence of dishing in which the upper surface of the circuit patterns containing the polysilicon films is dented in a dish shape, the occurrence of erosion by scraping off of the upper surface of the silicon nitride film between wiring lines, and the occurrence of a state in which the polysilicon film to be scraped off remains, so that the silicon nitride film between the circuit patterns is not exposed.

Although the polishing composition described in PTL 1 aims at the suppression of the dishing, the polishing removal rate of the polysilicon film remarkably decreases because the oxidant is contained. The CMP abrasive described in PTL 2 contains cerium oxide as abrasives. The cerium oxide is generally expensive and easy to precipitate, and therefore is inferior in storage stability.

The polishing composition described in PTL 3 contains the water-soluble polymer having a molecular weight of 300,000 or more, and therefore is not suitable for “the use of polishing a polishing object having a film containing a silicon material having a silicon-silicon bond formed on a pattern containing an insulating film by the CMP method to form circuit patterns containing the silicon material having a silicon-silicon bond”.

It is an object of the present invention to provide a polishing composition suitable for the use of polishing a polishing object having a film containing a silicon material having a silicon-silicon bond formed on a pattern containing an insulating film by a CMP method to form circuit patterns containing the silicon material having a silicon-silicon bond (the above-described problems are suppressed) and also capable of suppressing a remarkable reduction in polishing removal rate.

In order to solve the above-described problems, a polishing composition according to one aspect of the present invention contains abrasives, a first water-soluble polymer containing a polymer compound containing a lactam ring and having a weight average molecular weight of less than 300,000, a second water-soluble polymer containing a polymer compound containing a lactam ring and having a weight average molecular weight smaller than that of the first water-soluble polymer, a basic compound, and water.

The present invention can provide a polishing composition suitable for the use of polishing a polishing object having a film containing a silicon material having a silicon-silicon bond formed on a pattern containing an insulating film by a CMP method to form circuit patterns containing the silicon material having a silicon-silicon bond and also capable of suppressing a remarkable reduction in polishing removal rate.

