Polishing method and polishing apparatus permitting control of polishing time at a high accuracy
View Patent ↗A preceding wafer having an aluminum wiring and a silicon oxide film formed on an insulating film is chemico-mechanically polished. In the stage in which surface irregularities of the silicon oxide film are eliminated, polishing is discontinued. On the basis of the result, a polishing time is determined in accordance with the following formula: T =( D 1− D 2 )/ v+t 1 where, D 1 represents the thickness in the stage in which polishing is discontinued; D 2, a target thickness; t 1, a time required from the initial thickness to reach the thickness D 1; and the polishing rate of the material of the silicon oxide film formed on a flat substrate is denoted as v.
1. A polishing method of chemico-mechanically polishing a film formed on a wafer with a surface having surface irregularities to a target thickness, said method comprising the steps of:
determining a predicted required time for a former half of polishing by use of polishing data acquired upon polishing the preceding wafer selected from a same lot as a wafer to be polished and of a type similar to that of the wafer to be polished, the former half of polishing being for polishing the film until the surface irregularities disappear and are changed into a flat surface portion;
determining a predicted required time for a latter half of polishing by use of a polishing rate of the component materials of said film formed on a flat substrate, the latter half of polishing being for polishing the flat surface portion of the film;
using a value obtained by summing up these predicted required times; and
chemico-mechanically polishing a wafer to be polished.
2. A polishing method of chemico-mechanically polishing a film formed on a surface of a wafer having surface irregularities to a target thickness, said method comprising the steps of:
acquiring a polishing rate v of component materials of said film formed on a flat substrate;
chemico-mechanically polishing a preceding wafer selected from a same lot as a wafer to be polished and of the same type as the wafer to be polished, discontinuing polishing in a stage prior to reaching said target thickness so that the surface irregularities disappear, and measuring the film thickness in this stage;
calculating T as defined by the following formula (I):
T =( D 1 − D 2 )/ V+t 1 (I)
where, D 1 represents the film thickness upon discontinuing polishing; D 2 represents the target film thickness; and tl represents the time required from initial thickness to the thickness D 1 ; and chemico-mechanically polishing the wafer to be polished, using a value obtained with reference to T as the polishing time.
3. The polishing method according to claim 2 , wherein, upon chemico-mechanically polishing the wafer to be polished, T′ defined by the following formula (II) is used as the polishing time:
T′=T+d/v (II)
where, the difference in the initial thickness between said preceding wafer and said wafer to be polished is represented by d.
4. The polishing method according to claim 2 , wherein, for said preceding wafer of the target film thickness D 2 , said method further comprises a step of performing chemico-mechanical polishing with t 2 defined by the following formula as the polishing time:
t 2 =( D 1 − D 2 )/ v