CVD diamond-coated composite substrate containing a carbide-forming material and ceramic phases and method for making same

Abstract

The present invention relates to a composite material and the method of making same, which comprises a CVD diamond coating applied to a composite substrate of ceramic material and an unreacted carbide-forming material of various configurations and for a variety of applications. One example of the composite material is a composite of SiC and free silicon metal known as Reaction-Bonded Silicon Carbide. Several examples of applications of the invention include: 1) heads or disks for conditioning polishing pads, including pads used in Chemical-Mechanical-Planarization, 2) cutting and dressing tool inserts and tips, 3) heat spreaders for electronic devices, and 4) wear components including mechanical seals and pump seals.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material product comprising a layer of CVD diamond coating applied to a composite substrate of ceramic material and a carbide-forming material of various configurations and for a variety of applications, and methods for manufacturing these products. The products of the invention have utility in a wide variety of applications, which include: heads or disks for the conditioning of polishing pads, including pads used in Chemical-Mechanical-Planarization (CMP), cutting and dressing tool inserts and tips, wear components, such as mechanical seals and pump seals, and heat spreaders for electronic devices. 2. Description of Related Art CMP is an important process in the fabrication of integrated circuits, disk drive heads, nano-fabricated components, and the like. For example, in patterning semiconductor wafers, advanced small dimension patterning techniques require an absolutely flat surface. Afte...

AI Technical Summary

Benefits of technology

The present invention provides a composite material that overcomes shortcomings in conventional materials by using a composite ceramic substrate coated with CVD diamond. This composite material has advantages such as high adhesion of the diamond material to the substrate, being strong and tough, and being resistant to fracture at a low cost compared to conventional CVD diamond components. The invention also provides a method for reducing damage to CMP pads caused by conditioning heads by avoiding the presence of large diamond crystals on the surface of the conditioning head. The composite material can be used in applications such as CMP polishing pad conditioners, cutting tools, wear components, and heat distribution elements.

Problems solved by technology

CMP represents a major portion of the production cost for semiconductor wafers.

The total cost for the polishing pad, the downtime to replace the pad and the cost of the test wafers to recalibrate the pad for a single wafer polishing run can be quite high.

In many complex integrated circuit devices, up to five CMP runs are required for each finished wafer, which further increase the total manufacturing costs for such wafers.

With polishing pads designed for use with abrasive slurries, the greatest amount of wear on the polishing pads is the result of polishing pad conditioning that is necessary to place the pad into a suitable condition for these wafer planarization and polishing operations.

However, such over-texturing of the pad results in a shortening of the pad life.

On the other hand, under-texturing results in insufficient material removal rate during the CMP step and lack of wafer uniformity.

While the weave of these pads is quite dense, there is opportunity for slurry particles to become trapped within the weave.

Efficiency of removal of used slurry components must be balanced against damage to the fibers of the weave caused by contact with the conditioning head surface, which can cause excessive breakage of the fibers.

These pads also require conditioning, because the CMP polishing rate obtained when using the pads is highly sensitive to the surface properties of the abrasive.

Initial “breaking in” periods for these polishing pads, during which consistent quality polishing is difficult to obtain, tend to be long, and the resulting loss of wafers is an added expense.

The use of such conventional conditioning heads is limited to the conditioning of polishing pads that have been used during oxide CMP wafer processing, i.e. when the exposed outer layer of the polishing pad is an oxide-containing material as opposed to metal.

However, the conditioning heads described above are ineffective for conditioning polishing pads used in metal CMP processing, because the slurry used to remove metal from the wafer can react with the nickel and degrade and otherwise dissolve the nickel outer layer of the conditioning head.

Dissolution of the nickel overcoat can result in a major loss of the diamond grit from the plate, potentially scratching the wafers.

In addition, these typical conditioning heads use relatively large sized diamond grit particles.

However, a new generation CMP pads, including fixed abrasive pads and many woven pads, cannot be conditioned by conventional conditioners because conditioning heads having grit particles larger than 15 microns are too rough; the large grit particles tend to damage the pad.

However, difficulties with this approach are the lack of independent control of the particle size and density of working diamond grains, and the resulting bow of the diamond-coated silicon substrate product.

While silicon has been used successfully as a substrate for CVD diamond in preparation of some CMP pad conditioners, in accordance with the invention of this application, it has been found that a silicon substrate does not provide sufficient rigidity to support diamond coatings of sufficient thickness to provide optimal CMP conditioning in some applications with sensitive pad materials.

Because of both internal growth stress in CVD diamond materials, and the mismatch in thermal coefficients of expansion between diamond and silicon, a CVD diamond-coated silicon substrate conditioning head will bow or bend, even when supported by a metal backing plate, resulting in a conditioner that is not completely flat.

A bowed conditioning head does not provide as consistent conditioning as a flat conditioning head, and is thus less desirable.

However, this material is not well suited as a substrate for growing CVD diamond because the deposition process reduces the hardness and strength of the steel.

Cemented tungsten carbide is also used frequently in making cutting tools, but CVD diamond does not adhere well to this material without either etching of the surface to remove cobalt, or application of an intermediate layer of material to increase adhesion.

Likewise, silicon nitride, another material used in the cutting tool industry, does not provide the high adhesion necessary for CVD diamond coatings for viable commercial application.

Use of molybdenum as a substrate results in a high CVD diamond nucleation density, but again the adhesion of CVD diamond to this substrate is poor.

CVD diamond does adhere well to silicon substrates, but silicon is too fragile and has a fracture toughness that is too low, to make it suitable as a substrate for cutting tools, wear parts or other mechanical applications.

In many applications, however, the use of freestanding CVD diamond substrates is inhibited either by the size of the die, the thickness of the die needed for retrofit into existing packages, and / or the cost of the diamond material for the given application.

The high shear forces and temperatures that are generated in, for example, a dry-running pump seal application, generally result in adhesion failure of CVD diamond coatings on typical pump seal materials, such as sintered silicon carbide.

Images