60/054,907 filed August 6,1997.

BACKGROUND OF THE INVENTION Chemical-mechanical polishing (CMP) is used in the manufacture of semiconductor devices primarily for the planarization of device layers. Prior art CMP processes use single or multi-layered polishing pads. Typically, the multi-layered pads have a more rigid top layer than underlying layers as a means of incorporating the benefits of each type of pad.

During polishing or planarization it is often desirable to use pads with different degrees of flexibility to planarize or polish a single layer. Different textured pads are also needed during the processes. Process termination, and either changing the pad or removing the device to a different polishing machine, is necessary to change to pads of different morphology. The need exists for a pad system that would eliminate or reduce the duration of polishing process interruption for pad or machine changes.

SUMMARY OF THE INVENTION The present invention is directed to a polishing pad system comprising two or more layers and a means of adherence of the layers. The invention further comprises a means to vary the pad morphology during polishing or planarization with minimal process interruption. A preferred means is to have a compressible layer which can be pressurized or depressurized by a fluid to change the pad morphology.

DESCRIPTION OF INVENTION The present invention is directed to an improved polishing pad system useful in the polishing and planarization of substrates, particularly substrates for the manufacture of semiconductor devices or the like. The articles and methods of the present invention may also be useful in other industries and can be applied to any one of a number of materials, including, but not limited to, silicon, silicon dioxide, metal, dielectrics, ceramics and glass.

Surface planarization in semiconductor device manufacturing requires a polishing pad having the rigidity necessary for effective planarization and the resiliency required for the pad to conform to height variations present on the device surface. In addition, different pad textures are necessary for various polishing and planarization steps.

Some prior art polishing pads have multi-layers that, to some extent, provide the desirable characteristics of rigid and resilient pads. The top layer is generally firm and provides the pad's planarization ability. The lower layer or layers are generally more resilient or elastic and allow the pad to conform to surface feature height variations.

Resiliency and elasticity also reduce the edge effect which is the creation of unusable portions on the edge of a semiconductor wafer by non-uniform surface removal during polishing or planarization. Although prior art layered pads combine rigid and resilient properties, the overall effect is constant for a specific pad. Likewise, texture and other pad morphology is constant. Morphology as used herein refers to characteristics such as elasticity, resiliency, texture, porosity and any other pad characteristic that affect polishing or planarization performance. An advantage of the present invention is that these characteristics are variable, with little or no interruption to the polishing or planarization process.

Typically, the planarization or polishing process comprises, 1) attaching a polishing pad to a platen; 2) introducing a polishing fluid onto the platen; 3) bringing a workpiece in close proximity to the pad; and 4) having the pad and workpiece move in relation to one another. The polishing pad may be attached to the platen by a variety of means including, but not limited to, mechanical clamping, adhesive backing or a vacuum drawn through the platen.

As the process progresses it is often desirable to alter the degree of pad resiliency, elasticity, texture or other morphology. This is typically done by changing the pad or transferring the workpiece to a different machine. The present invention eliminates or reduces the duration of this process interruption by providing variable characteristics in a single pad.

Polishing pads of the present invention preferably comprise a top layer, capable of being deformed to varying degrees over one or more lower layers. These lower layers may have different characteristics such as textures, porosities, elasticities or resiliencies.

Virtually any material having the desired morphology may be used as a layer and be in keeping with the present invention.

Examples of materials that can provide texture are replicated-reticulated foams, spun-bonded polyester or mesh material, but a variety of other materials may also be used. Variations in surface texture depths may be achieved by a combination of textured materials or from a single material. Some materials that provide elasticity or resiliency include compressible and resilient composites, replicated foams, poromerics, textured leathers (natural and synthetic), perforated or punctured films, reticulated materials, woven textiles, felts, paper and sponges. Impermeable or semipermeable top layer materials include, but are not limited to, composites, closed cell foams, films (any kind), paper, plastics and metals.

The present invention include a means for adhering the layers to one another.

The pad layers may be laminated to one another by adhesive or similar means, or may adhere to one another by a vacuum drawn from the bottom layer through the upper layers. It is also possible to use mechanical, electrostatic or magnetic forces for layer adhesion. Layers that are not adhered by adhesives may be removed with little effort and replaced with layers of alternative characteristics. For instance, layers held together by a vacuum may be easily separated upon release of the vacuum. This significantly reduces the interruption of the planarization or polishing process The lamination techniques described above (with the exception of adhesives) may also be used as a means to vary the morphology of the pads. In a preferred embodiment of the present invention, the polishing pad comprises an impermeable or semipermeable top layer, having a polishing surface, and one or more gas permeable layers below, including a cellular layer and a reticulated layer. The pad is adhered to the platen by drawing a vacuum through the lower layer. The vacuum also serves to adhere the pad layers to one another. By varying the strength of the vacuum, the pad's resiliency, texture and other morphology can be controlled, thereby altering the pad's polishing and planarization capabilities. The vacuum serves to deplete the air in the cellular material, thereby compressing the layer and reducing resiliency and elasticity.

Further more the vacuum draws the impervious top layer onto the reticulated layer. As the impervious layer deforms, the texture of the reticulated layer is imparted to the impervious layer. By varying the strength of the vacuum, the degree of resiliency and texture can be varied. Variations may be made during polishing or planarization without

removal of the workpiece or the pad. In an alternative embodiment, temperature variations affect the pad's morphology by causing expansion and contraction. The pad's polishing ability is also enhanced by the effect of the temperature increase on the process..

Vacuum, temperature, mechanical force, electrostatic force or magnetic force variations may be controlled manually or by a microprocessor programmed to vary the pad characteristics at certain intervals. A microprocessor may also be used in conjunction with surface roughness and planarization measuring devices to provide continually variable pad characteristics, specific to the polishing or planarization needs at any given time. In a preferred embodiment a micro-electro-mechanical system is employed to detect polishing progress and process needs and adjust the pad morphology accordingly.

Other means of layer adhesion may also be controlled manually or electronically to provide variable pad characteristics with minimal process interruption.

As used in the claims, the term"polish"or any form thereof, is intended to include"planarize"or any corresponding form thereof.