Method of coating a silicon or silicide substrate

Details Method of coating a silicon or silicide substrate Method of coating a silicon or silicide substrate

1995-06-05

2001-08-14

Meeks, Timothy (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Pretreatment of substrate or post-treatment of coated substrate

C427S554000, C427S555000, C427S556000, C427S595000, C427S596000, C427S597000, C427S248100, C427S255400

Reexamination Certificate

active

06274206

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to the treatment of substrates, for example metal substrates, the treatment including forming materials on a surface of the substrate, and to the formation of physical object structures.
BACKGROUND OF THE INVENTION
The present invention relates to a broad range of processes, including those for the enhancement and modification of objects, such as substrates, as well as to the fabrication of object structures. For example, it is known to coat a substrate to enhance the utility of the substrate. By way of further example, it is known to construct a physical representation of a three-dimensional object stored in a computer memory. These and additional fields of endeavor are discussed in greater detail hereinbelow.
Commercially and economically enhancing, modifying, and/or fabricating objects having a predetermined composite material is highly desirable in many industries, including mechanical and electronic industries. For example, treating a substrate (e.g. applying a diamond or a diamond-like carbon coating) may be desirable to enhance the performance or to expand the applications of the original object. Also, fabricating an object (e.g. rapid prototyping) may be desirable to evaluate an object prior to production.
Prior art methods and apparatus for treating substrates and/or fabricating objects are, however, limited in their application. Although the industry is attempting to overcome these limitations, prior art technologies have struggled to establish an effective process, having a wide range of capabilities, to commercially and economically treat and/or fabricate an object having a desired composite material (e.g. diamond or DLC).
The following is a discussion illustrating the demand for treatment of a surface in the engineering component industry. However, it should be appreciated that these demands also exist in other industries, such as semiconductor packaging and fabrication, surgical, home appliance, and other industries where it may be desirable to improve the performance of an existing object.
Manufacturing processes, for example cutting, stamping, forming have long been an exemplary area of interest for coating the surface of a relatively soft tool with a relatively hard coating material. The development and application of scratch resistant coatings to softer underlying substrates is another exemplary area of prolonged endeavor. The development and application of low-friction coatings is yet another exemplary area of prolonged endeavor. Other areas of interest are in machining, tooling, electronic components, and surgical components.
One area of particular interest is the application of diamond and diamond-like carbon (DLC) to machine tools (e.g., to machine tool cutting inserts). Diamond and DLC are especially tough (hard) materials, wear well, and have thermal qualities which are beneficial in many applications. For many machining applications, the qualities of diamond or DLC are unsurpassed by any other available material. The application of a diamond or DLC to a cutting tool is discussed herein as exemplary of the state of the art in substrate coating technology and as an example of broad range of uses to which the present invention is applicable.
Metal-cutting, or machining, is performed with tools operating on a workpiece. Typically, a tool is rotated and brought to bear upon a workpiece to remove material from the workpiece. The tool may be provided with integral cutting edges, or it may be formed as a carrier for cutting inserts, such as carbide inserts, having one or more cutting edges. Among the numerous factors and considerations that typically are taken into account when machining, more particularly in the choice of tools for machining, are the nature of the material (workpiece) sought to be machined, as well as the following parameters relating to the tool itself:
“tool speed” (typically measured in meters-per-minute, or in feet-per-minute);
* “feed rate” (typically measured in millimeters(or inches)per-revolution);
“depth of cut”, or “DOC” (typically measured in millimeters and inches);
“length of cut” (typically measured in millimeters, or in inches); and
lubrication (e.g., versus “dry” machining).
Additionally, the following factors are important considerations when machining (e.g., drilling, reaming, milling, end-milling, surface-finishing) a workpiece:
resulting surface finish (typically measured in &mgr;in) that will be achieved on the workpiece;
tool life;
abrasion resistance of the tool;
thermal conductivity of the tool;
chemical and thermal stability of the tool; and
tool coefficient of friction.
Carbide has long been an established choice for use in cutting tools and inserts, especially for cutting (machining) ferrous, nonferrous or abrasive materials such as aluminum and its alloys, copper, brass, bronze, plastics, ceramics, titanium, fiber-reinforced composites and graphite. Various forms of carbide are known for tools and inserts, such as cobalt-consolidated tungsten carbide (WC/Co).
In recent years, polycrystalline-diamond (PCD) brazed-tip cutting tools have demonstrated their feasibility. These PCD cutting tools generally offer only one cutting edge, and require relatively high temperature and pressure processes for their fabrication. PCD tool inserts may have a relatively thick diamond layer (2.5 mm is a common thickness). A shortcoming of PCD is that the cobalt binder of a PCD tool can react chemically with certain work materials. PCD appears to be beneficial for the machining of high-silicon aluminum alloys and other highly abrasive materials.
In certain applications, however, for example in the machining of carbon phenolic composite material, uncoated carbide and polycrystalline diamond tools (PCD) have proven to be unsatisfactory. Aluminum oxide (as opposed to diamond) inserts have been shown to be more effective for machining this particular material.
More recently, thin-film-diamond-coated inserts, and thick-film-diamond brazed-tip tools are being developed for machining applications. Generally, a “thin” film is a film that is less than 100 &mgr;m (micrometers) thick.
An example of a thick-film-diamond brazed tool, using chemical vapor deposition (CVD), is the “DT-100” (from Norton Diamond Film of Northboro, Mass.), wherein a diamond or DLC is grown on a disc having diameter of eight inches or less, then laser cut to shape, and then brazed to a carbide shank.
An example of a thin-film-diamond coated carbide insert is the “DCC” (from Crystallume, Menlo Park, Calif.), which has demonstrated a tool life 10-15 times greater than conventional coated carbide in applications turning highly abrasive 390 alloy aluminum. This diamond-coated insert is made by a chemical vapor deposition (CVD) process, and is reported to outperform uncoated carbide and perform equally to or better than PCD tools. The CVD process employed is reportedly a microwave plasma enhanced (MPE) CVD process which takes place at relatively low temperatures and pressures (as compared with conventional PCD fabrication methods which utilize High Pressure and High Temperature (“HPHT”) techniques. Using these processes, any insert shape can reportedly be uniformly coated, and the coated inserts can have sharp edges and chip-breaker geometries. Hence, these inserts are indexable and can provide from two-to-four cutting corners. CVD-coated tools tend to have a thin diamond layer (typically less than 0.03 mm), which tends to allow the toughness of the underlying substrate material to dominate in determining overall tool strength, even when shock-loaded. Hence, these CVD (e.g., “DCC”) inserts tend to be able to handle a larger DOC.
For example, a 30% carbon phenolic composite material has successfully been machined using thin-film-diamond-coated silicon nitride inserts.
A critical concern with any coated tool or insert is that the coating should exhibit good adhesion to the underlying base material (e.g., carbide). Concerns with the prior art include:
delamination (catastrophic failure);
adhesive and abrasi

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