In recent years, as semiconductor devices are made highly integrated and highly dense, circuit interconnections have become finer and the number of layers of multi-layer interconnections has been increased. Aiming at achieving multi-layer interconnection while aiming at finer circuitry leads to film coverage of step geometry (step coverage) being lowered in thin film formation as the number of the interconnected layers increases because surface steps increase while following surface irregularities on a lower layer. Therefore, in order to obtain multi-layer interconnection, this step coverage has to be improved to perform a planarization process at an appropriate time. In addition, since finer optical lithography entails shallower depth of focus, it is necessary to subject a surface of a semiconductor device to the planarization process so that surface steps of irregularities on the surface of the semiconductor device fall within the depth of focus. As the circuitry is made finer, a requirement for accuracy with respect to the planarization process has been raised. Not only in a multi-layer interconnecting process but also at a FEOL (Front End Of Line), as a transistor's peripheral structure is complexed, the requirement for accuracy with respect to the planarization process has been raised.
In this way, in a manufacturing process of the semiconductor device, a planarization technique for the semiconductor device surface has become important more and more. In this planarization technique, the most important technique is chemical mechanical polishing (CMP). This chemical mechanical polishing is a process in which a polishing apparatus is used to perform polishing by supplying a polishing liquid containing abrasive grains such as of silica (SiO2) onto a polishing surface of a polishing pad or the like and bringing a substrate such as a semiconductor wafer into sliding contact with the polishing surface.
This type of polishing apparatus includes a polishing table having a polishing surface formed of a polishing pad, and a substrate holder, called a top ring or a polishing head, for holding the semiconductor wafer. In a case where such a polishing apparatus is used to polish the semiconductor wafer, the semiconductor wafer is held by the substrate holder and the semiconductor wafer is pressed against the polishing surface at a predetermined pressure. At this time, the polishing table and the substrate holder are moved relatively to each other such that the semiconductor wafer is brought into sliding contact with the polishing surface to polish the surface of the semiconductor wafer to a flat and mirror finish.
In such a polishing apparatus, if a relative pressing force between the semiconductor wafer and the polishing surface of the polishing pad during polishing is not uniform over the entire surface of the semiconductor wafer, insufficient polishing or excessive polishing would occur depending on the pressing force applied to any portion of the semiconductor wafer. In order to unify the pressing force applied to the semiconductor wafer, a pressure chamber formed of an elastic membrane (membrane) is provided at a lower part of the substrate holder, and, by supplying a fluid such as pressurized air to this pressure chamber, the semiconductor wafer is pressed against the polishing surface of the polishing pad by means of a fluid pressure via the elastic membrane to perform polishing.
The substrate holder is provided with a retainer ring surrounding the semiconductor wafer (e.g., see Patent Literature 1), and when polishing the semiconductor wafer, the retainer ring is pressed against the polishing surface at a predetermined pressure so that the semiconductor wafer held by the substrate holder does not get out of the polishing head. Here, a pressing force of the retainer ring is also an adjustment parameter for adjusting a polishing profile of a periphery of the semiconductor wafer.
As the pressing force of the retainer ring is lowered, a phenomenon cannot be prevented that the retainer ring on a downstream side of table rotation is uplifted by a horizontal force from the wafer caused by friction between the wafer and the polishing pad and the semiconductor wafer during polishing cannot not be held, and thereby, the semiconductor wafer slides on the polishing pad to get out to the outside (hereinafter, referred to as sipping out) at a certain pressing force of the retainer ring (hereinafter, referred to as retainer ring pressure). In order that the semiconductor wafer does not slip out, the retainer ring pressure needs to be set to be equal to or more than a lower limit of retainer ring pressure (hereinafter, also referred to as RRP (retainer ring pressure) lower limit) at which the semiconductor wafer can be polished without slipping out. However, the RRP lower limit varies depending on a process type or a polishing condition, and thus, disadvantageously is difficult to determine.
As for dealing with this problem, there may be considered a method in which polishing is actually performed so as to lower the pressing force of the retainer ring until the semiconductor wafer slips out to measure the RRP lower limit. However, in this method, because the semiconductor wafer actually slips out, expendables such as the membrane or the retainer ring may be broken in some cases. Such a method would require time also. Further, the RRP lower limit varies depending on the process type or the polishing condition, which involves a need to conduct a test for finding the RRP lower limit every time the process type or the polishing condition is changed. However, it is not realistic to conduct a test for finding the RRP lower limit every time the process type or the polishing condition is changed, considering time and effort are taken.
It is desired to provide a polishing apparatus, a control method and, a recording medium capable of preventing an polishing object from slipping out without depending on the process type or the polishing condition.
A polishing apparatus according to one aspect of this technique, a polishing apparatus for polishing a surface to be polished of an polishing object by sliding the surface to be polished and a polishing member relative to each other, comprising: a pressing unit that presses a back surface of the surface to be polished of the polishing object such that the surface to be polished is pressed against the polishing member; a retainer member that is arranged on an outer side of the pressing unit and presses the polishing member; a storage unit that stores information concerning a condition for preventing the polishing object from slipping out, the condition being defined by use of information concerning a pressing force of the retainer member; and a control unit that acquires information concerning a force of friction between the surface to be polished of the polishing object and the polishing member or information concerning the pressing force of the retainer member, and executes control for adapting to the condition for preventing the slipping-out by using the acquired information concerning the force of friction or the acquired information concerning the pressing force of the retainer member.
By doing so, the condition for preventing the polishing object from slipping out is not changed even if the process type or the polishing condition is varied, which makes it possible to prevent the polishing object from slipping out without depending on the process type or the polishing condition.
A control method according to one aspect of this technique, a control method for executing control by way of referencing a storage unit that stores information concerning a condition for preventing an polishing object from slipping out, the condition being defined by use of information concerning a pressing force of a retainer member, the method comprising: a step of acquiring information concerning a force of friction between a surface to be polished of the polishing object and a polishing member, or the information concerning the pressing force of the retainer member; and a step of executing control for adapting to the condition for preventing the slipping-out by using the acquired information concerning the force of friction or the acquired information concerning the pressing force of the retainer member.
By doing so, the condition for preventing the polishing object from slipping out is not changed even if the process type or the polishing condition is varied, which makes it possible to prevent the polishing object from slipping out without depending on the process type or the polishing condition.
A recording medium according to one aspect of this technique, a recording medium storing therein in a non-transitory manner a program for executing control by way of referencing a storage unit that stores information concerning a condition for preventing an polishing object from slipping out, the condition being defined by use of information concerning a pressing force of a retainer member, the program causing a computer to execute: a step of acquiring information concerning a force of friction between a surface to be polished of the polishing object and a polishing member, or the information concerning the pressing force of the retainer member; and a step of executing control for adapting to the condition for preventing the slipping-out by using the acquired information concerning the force of friction or the acquired information concerning the pressing force of the retainer member.
By doing so, the condition for preventing the polishing object from slipping out is not changed even if the process type or the polishing condition is varied, which makes it possible to prevent the polishing object from slipping out without depending on the process type or the polishing condition.