Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-04-11
2001-12-25
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S527000, C451S533000
Reexamination Certificate
active
06332832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CMP (Chemical Mechanical Polishing) pad used in chemically and mechanically polishing a work such as a semiconductor substrate (wafer), and a CMP processing apparatus using the same.
2. Description of Related Art
In a process of producing semiconductor devices, such a treatment is carried out that makes a wafer surface flat and smooth as required. The chemical and mechanical polishing (CMP) process has come to be regarded as a promising process for making a wafer surface smooth and flat.
A CMP processing apparatus comprises a polish head that rotates while holding a wafer, a polish pad disposed to face the polish head, a platen that holds the polish pad, and a slurry supply unit that supplies a polishing medium (slurry) including a chemical liquid and abrasive particles (made of alumina, for example) onto the polish pad. With this constitution, when a wafer is pressed against the polish pad while rotating the polish head, the surface of the wafer is chemically and mechanically polished by the actions of the chemical liquid and the abrasive particles. The platen is adapted to move along the wafer surface, so that the polishing operation is carried out while changing the contact position between the polish pad and the wafer.
The polish pad has such a laminated structure as, for example, a hard pad having a relatively high coefficient of elasticity is laminated on a soft pad having a relatively low coefficient of elasticity. The coefficient of elasticity with respect to compression in the direction of pressing against the wafer to be polished is uniform throughout the pad surface.
Another polish pad of such a configuration has been proposed as the so-called fixed abrasive particles type where abrasive particles are fixed onto the pad surface. In this case, it suffices to supply only a chemical liquid onto the polish pad. The polish pad of this constitution comprises abrasive particles of substantially the same size and the same shape disposed on the pad surface to be uniformly distributed thereon, with all abrasive particles making contact with the wafer under substantially the same condition.
With the polish pads described above, condition of contact with the work being polished is constant throughout the pad surface. Although this constitution has such an advantage that the surface of the work can be polished uniformly, it may not necessarily provide advantage at all times since only a certain fixed condition of polish can be achieved.
In case it is desired to polish roughly at a high polishing rate in an early stage of the polishing process and carry out fine polish in the last stage of the polishing process, for example, the polish pad must be changed in the course of the polishing process. In practice, it is required to transfer the wafer from one CMP processing apparatus to another CMP processing apparatus. This may result in more complex and larger production apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a CMP polish pad capable of achieving polished states of a plurality of types with a single CMP polish pad.
Another object of the present invention is to provide a CMP processing apparatus capable of achieving polished states of a plurality of types with a single CMP pad.
The CMP pad of the present invention has at least two types of polishing portions, having different contact conditions with the work to be polished, provided on the pad surface.
In the constitution described above, polishing portions of at least two types are provided on the pad surface having different contact conditions with the work to be polished. Accordingly, two or more types of polished states can be achieved.
Such a constitution may be employed, for example, as the polishing portions of at least two types include polishing portions of a plurality of types having different coefficients of elasticity with respect to compression in the direction of pressing against the work to be polished.
The polishing portions of at least two types may also include polishing portions of a plurality of types having different areas of contact with the work to be polished.
The polishing portions of at least two types may also include polishing portions of a plurality of types having different heights above the pad surface.
The polishing portions of at least two types may also include polishing portions of a plurality of types having different shapes of contact areas with the work to be polished.
Such a constitution may be employed, for example, as a polishing portion of high coefficient of elasticity and a polishing portion of low coefficient of elasticity are provided, with the polishing portion of high coefficient of elasticity being formed to be lower than the polishing portion of low coefficient of elasticity in height. In this case, when the work to be polished is pressed hard against the polish pad, the work can be polished by both the polishing portion of high coefficient of elasticity and the polishing portion of low coefficient of elasticity. It is also made possible to put only the polishing portion of low coefficient of elasticity into contact with the work by decreasing the force of pressing the work against the polish pad. This makes it possible to achieve two types of polished state by controlling the pressing force.
For this purpose, for example, area of the polishing portion of high coefficient of elasticity in contact with the work may be set greater than the area of the polishing portion of low coefficient of elasticity in contact with the work. Thus two kinds of polished states can be achieved: rough polish using both the polishing portions of high coefficient of elasticity and the polishing portion of low coefficient of elasticity, and fine polish using only the polishing portion of low coefficient of elasticity.
Such a constitution may also be employed as the surface of the polishing portion of high coefficient of elasticity that makes contact with the work to be polished is made in a shape having sharp edges (for example, straight edges) and the surface of the polishing portion of low coefficient of elasticity that makes contact with the work to be polished is made in a relatively smooth shape (for example, a shape that has only smoothly curved edges or a curved surface without any edges). Thus two kinds of polished states can be achieved: rough polish using both the polishing portion of high coefficient of elasticity and the polishing portion of low coefficient of elasticity, and fine polish using only the polishing portion of low coefficient of elasticity.
Each polishing portion may also comprise a contact portion that touches the work and an elastic body that carries the contact portion on the pad surface. In this case, the polishing portion of high coefficient of elasticity and the polishing portion of low coefficient of elasticity can be formed by setting the coefficient of elasticity of the elastic body to appropriate values. Also height of each polishing portion can be set by setting the height of the elastic body and/or the contact portion to appropriate value.
The contact portion that makes contact with the work may be made of a urethane pad or the like, or comprise abrasive particles made of such a material as alumina, silica or cerium oxide.
The polishing portion of each type is preferably distributed substantially uniformly over the pad surface.
This constitution makes it possible to achieve satisfactory polished state since the surface to be polished of the work can be polished uniformly with the polishing portion of each type.
Polishing portions of individual types are preferably disposed, for example, in a symmetrical arrangement on the pad surface. Specifically, the polishing portions of each type may be disposed in a centrosymmetrical arrangement with respect to the center of the pad surface or axisymmetrial arrangement with respect to the centerline of the pad surface.
The CMP processing apparatus according to the present invention comprises the CMP po
Arent Fox Kintner & Plotkin & Kahn, PLLC
Hail III Joseph J.
Ojini Anthony
Rohm Company, Ltd.
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