(19) United States (12) Patent Application Publication (10) Pub. No.: US 2004/0065022 A1
Machii ct al. (43) Pub. Date: Apr. 8, 2004
(54) POLISHING COMPOUND AND METHOD Dec. 28, 2001 (JP) .................................... .. 2001-400872 FOR POLISHING SUBSTRATE Dec. 28, 2001 (JP) .................................... .. 2001-400876
Dec. 28, 2001 (JP) . . . . . . . . . .. 2001-400882
(76) Inventors: Youichi Machii, Ibaraki-ken (JP); Dec. 28, 2001 (JP) .................................... .. 2001-400888 Naoyuki Koyama, Ibaraki-ken (JP); Dec. 28, 2001 (JP) .................................... .. 2001-400891 Masaya Nishiyama, Ibaraki-ken (JP); Masato Yoshida, Ibaraki-ken (JP) Publication Classi?cation
Correspondence Address: (51) Int. Cl.7 .B24B 1/00; C09G 1/02; C09G 1/04 ANTONELLI, TERRY, STOUT & KRAUS, (52) US. Cl. .............. .. 51/309; 106/3; 438/692; 438/693 LLP 1300 NORTH SEVENTEENTH STREET (57) ABSTRACT
V A 22209 9889 Us Apolishing slurry and a polishing method Which are suitably - ( ) used in a CMP technique for ?attening a surface of a
_ substrate in a production process of a semiconductor device. (21) Appl' NO" 10/467,864 The polishing slurry comprises particles and a medium in (22) PCT Filed: Feb 20 2002 Which at least a part of the particles are dispersed, Wherein
the particles are made of at least one of (1) a cerium (86) PCT No; PCT/JP02/01483 compound selected from cerium oxide, cerium halide and
cerium sul?de and having a density of 3 to 6 g/cm3 and an (30) Foreign Application Priority Data average particle diameter of secondary particles of 1 to 300
nm and (2) a tetravalent metal hydroxide. A polishing Feb. 20, 2001 (JP) ....................................... ..2001-44252 method using the polishing slurry takes advantage of a Jun. 28, 2001 (JP) .................................... .. 2001-197274 chemical action of particles in the polishing slurry and Nov. 15, 2001 (JP) 2001-350598 minimizes a mechanical action of the particles, thereby Nov. 15, 2001 (JP) .................................... .. 2001-378838 achieving a decrease in scratches caused by the particles and Dec. 21, 2001 (JP) .................................. .. 2001-4000866 an increase in polishing rate at the same time.
US 2004/0065022 A1
POLISHING COMPOUND AND METHOD FOR POLISHING SUBSTRATE
 The present invention relates to a polishing slurry Which is suitably used in a technique for producing a semiconductor device and a method of polishing a substrate by use of the polishing slurry.
 In a current production process of a ULSI semi conductor device, processing techniques for achieving a higher density and a higher degree of integration are under study and development. As one of such processing tech niques, a CMP (Chemical Mechanical Polishing) technique has been gaining ground as a technique absolutely required for ?attening of an interlayer insulating ?lm, formation of shalloW trench isolation, and formations of plugs and implanted metal Wiring, in a production process of a semi conductor device.
 In a conventional production process of a semicon ductor device, silica (SiO2)-based particles and ceria (CeO2)-based particles have been Widely used as abrasive of a CMP slurry for ?attening an inorganic insulating ?lm layer such as a silicon oxide insulating ?lm Which is formed by such a method as plasma CVD or loW pressure CVD. A representative example of the silica-based abrasive is fumed silica. The fumed silica is produced by dispersing particles Which has been groWn by such a method as thermal decom position of silicon tetrachloride, into a medium and then adjusting the pH of the solution. Polishing of an insulating ?lm layer by use of a fumed silica abrasive has a problem that a polishing rate is loW.
 A representative example of the ceria-based abra sive is cerium oxide. The most outstanding feature of a cerium oxide abrasive is a high polishing rate Which cannot be achieved by the silica-based abrasive. A ceria-based compound having a high valence such as cerium oxide, as knoWn as a strong oxidiZing agent, has a characteristic of being chemically active. Thus, its chemical action as an oxidiZing agent and a mechanical removing action of par ticles interact With each other. It is believed that the cerium oxide abrasive thereby exhibits the high polishing rate.
 The cerium oxide particles are loWer in hardness than silica particles or alumina particles and therefore hardly make scratches on a surface to be polished. Hence, it is useful for giving a mirror ?nish to a surface to be polished. The cerium oxide abrasive is used for, for example, polish ing a glass surface.
 Taking advantage of these characteristics, the cerium oxide abrasive has been becoming Widely used as a CMP abrasive for an insulating ?lm of a semiconductor. This technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 270402-1997. In recent years, along With an increase in the number of layers constituting a semiconductor device and an increase in the degree of integration of the semiconductor device, further increases in a yield and throughput of the semiconductor device have been increasingly demanded. Along With that, faster polish ing Which causes no scratches has been increasingly desired in a CMP process.
Apr. 8, 2004
 HoWever, if the cerium oxide abrasive for polishing a glass surface is used for polishing an insulating ?lm of a semiconductor as it is, particle diameters of its primary particles are so large that visibly observable scratches are made on the surface of the insulating ?lm due to the large primary particle diameter When the surface is polished so vigorously as to attain a suf?ciently high polishing rate. A decrease in the particle diameter of the primary particle can decrease the scratches but also loWers the polishing rate at the same time. In the case of cerium oxide, it is believed that the processing is caused to proceed by its chemical action and a mechanical removing action by particles, and the mechanical removing action by the particles causes scratches.
 Thus, as a method for further decreasing scratches in a CMP process using the cerium oxide abrasive, an abrasive improving method such as a selection of the concentration or density or particle diameters of primary particles of the abrasive to cause a desired polishing rate and a surface condition Without scratches, or a process improv ing method such as a reduction in a polishing pressure or a decrease in the rotation speed of a surface plate may be used. HoWever, in any of these methods, there arises a problem that a polishing rate loWers, and it has been considered dif?cult to achieve a further increase in the polishing rate and a further decrease in the occurrence of the scratches at the same time. In the future, as the number of layers constituting a semiconductor device and the degree of integration of the semiconductor device are further increased, a polishing slurry Which causes no scratches and can achieve fast polishing Will be absolutely required to improve a yield of the semiconductor device.
 Recently, not only to attain a high polishing rate but also to facilitate shalloW trench isolation, a polishing slurry With a large ratio betWeen a polishing rate for a silicon oxide insulating ?lm and a polishing rate for a silicon nitride insulating ?lm is demanded. Further, there has been a problem that the pH of a polishing slurry changes With time during polishing or storage and the change in the pH loWers a polishing rate.
 In addition, there has been a case Where abrasive dispersed in a polishing slurry exhibit instable dispersibility by settling or agglomeration. In evaluating such dispersion stability of the polishing slurry, the dispersion stability has been dif?cult to evaluate in numerics since particle diam eters of the dispersed particles are small and a degree of settling cannot be recogniZed visually.  The present invention provides a polishing slurry Whose abrasives, together With a surface to be polished such as a silicon oxide insulating ?lm, form a chemical reaction layer and Which is capable of polishing the layer While achieving an increase in polishing rate and a reduction in scratches at the same time, and a method of polishing a substrate by use of the polishing slurry.
 Further, the present invention provides a polishing slurry Which can achieve fast polishing With good reproduc ibility by suppression of a change in its pH With time, has a large ratio betWeen a polishing rate for a silicon oxide ?lm and a polishing rate for a silicon nitride ?lm, has particles favorably dispersed therein so as to reduce occurrences of settling and agglomeration, and has dispersibility detectable and controllable by a variety of optics, and a method of polishing a substrate by use of the polishing slurry.