Patent Application
20120264303
The disclosure is related to a system, method and slurry used in chemical mechanical polishing (CMP) of semiconductor devices.
Chemical mechanical polishing, CMP, is commonly used in the semiconductor manufacturing industry to polish and remove metal or other materials from over a surface of a semiconductor substrate upon which semiconductor devices are being fabricated. Most commonly, conductive interconnect patterns are formed on semiconductor devices by forming a series of openings, such as vias and trenches in an insulating material disposed on a substrate surface, and then forming a conductive layer over the substrate surface and filling the openings. Damascene technology involves removing the conductive material from over the surface such that the conductive material remains only in the openings to form conductive structures such as various plugs and leads that serve as interconnection patterns and vias. CMP is also used extensively for planarizing shallow trench isolation regions.
When polishing to remove metal materials from over the substrate surface, it is critical to ensure that no metal residue remains over the surface as this can cause bridging between otherwise isolated conductive features, resulting in short circuits. It is also critical to ensure that dishing is avoided. Dishing involves the formation of a concave surface in the top surface of the conductive feature and can create topography problems in subsequent processing.
One way to prevent the occurrence of defects such as the aforementioned defects, is to ensure that the metal removal rate is uniform and consistent during polishing and does not diminish over time. During polishing, the metal removal rate depends on a number of factors including but not limited to the chemistry of the polishing solution, the amount of oxidation caused by the chemistry of the polishing slurry, and the degree of mechanical wearing caused by the abrasives in the slurry.
Common drawbacks of current polishing technologies include inconsistent metal removal rates and polishing rates that do not remain constant over time.
The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not necessarily to scale. On the contrary, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. Like numerals denote like features throughout the specification and drawing.
The disclosure provides a polishing slurry advantageously used in the chemical mechanical polishing of metal materials or other materials, in the semiconductor manufacturing industry. In addition to copper and aluminum, the slurry may be used for polishing other materials, such as silicon dioxide, tungsten, or carbon nanotubes. The polishing slurry includes a chemical solution and abrasives. The polishing slurry may be used in the chemical mechanical polishing of various metals, metal alloys and other conductive and semiconductor materials and may be referred to as a metal polishing slurry in some embodiments. The polishing slurry is chemically reactive toward metal or other material being polished, and may include surfactants, oxidizers, metal corrosion inhibitors, enhancers, and other suitable materials that are used in polishing slurries. The polishing slurry includes abrasive particles and, in some embodiments, the abrasive particles are present in a bimodal or multimodal distribution. There may be two prevalent different particle sizes among the particles that make up the abrasives or there may be two prevalent particle size ranges among the particles that make up the abrasives. There may be a bimodal distribution of abrasive particles in which there are two predominant populations of particles, one population representing a first range of particle sizes and another population representing a second range of particle sizes.
The disclosure also provides a method for removing metal or another conductive or non-conductive material from over the surface of a semiconductor substrate by polishing using the slurry. Also provided is a system including a CMP polishing tool, a semiconductor wafer with metal or another conductive material formed over the surface thereof, and the aforementioned polishing slurry.
Provided is a polishing slurry useful in CMP operations for polishing various metals, alloys or other conductive materials, or dielectric materials (such as silicon dioxide). According to some embodiments, during the CMP operation using the polishing slurry to remove metal, metal is removed from over a surface of a semiconductor substrate. The metal may advantageously be formed over a dielectric or insulating layer that includes openings therein. The openings may be in the form of contacts, vias, trenches and other openings. The polishing operation may be used to remove the metal material from over the surface such that the metal remains only in the openings to form structures such as plugs and leads that serve as interconnection patterns, contacts and vias in accordance with damascene processing technology. The metal may be any of various metals used in semiconductor manufacturing including but not limited to copper, aluminum, molybdenum, tungsten, tantalum, and other suitable metal materials and metal alloys.
The polishing slurry includes a chemical solution and abrasives. The polishing slurry may be a metal polishing slurry that is chemically reactive toward the metal material it is used to remove but may also include oxidizers or other components that reduce the metal polishing rate. According to various exemplary embodiments, the polishing slurry may include surfactants, oxidizers, metal corrosion inhibitors, enhancers, and abrasives. The surfactants may be formed of alkylphenol ethoxylates and their derivatives, the oxidizers may be peroxide or other suitable materials, the metal corrosion inhibitors may be benzotrialole or its derivatives and the enhancers may be glycine or related amino acids. It should be understood that the proceeding examples are intended to be exemplary only and other surfactants, oxidizers, metal corrosion inhibitors and enhancers may be used in other exemplary embodiments and further components may also be included in the polishing slurry.
The abrasives are particles that may be formed of silica, including fumed silica or colloidal silica according to exemplary embodiments. In other exemplary embodiments such as in slurries directed to polishing/removing copper, the abrasive particles may be formed of Al2O3 or other suitable materials. One aspect of the disclosure is that the abrasives in the polishing slurry are characterized by a bimodal distribution of particle sizes. The abrasives in the polishing slurry may also be characterized as including a prevalence of two different sized particles or two different ranges of particle sizes that are most prevalent. By prevalence of two particle sizes or two ranges of particle sizes, it is meant that each of two particle sizes or ranges of particle sizes, is present in a population much greater than the population of any other particle size or particle size range, although relative populations may vary. In one exemplary embodiment, the population of each of the most prevalent particle sizes or ranges may be at least 60% greater than any other particle size or particle size range, but this is intended to be exemplary only. In one exemplary embodiment, the population of each of the most prevalent particle sizes or ranges may be at least 40% greater than any other particle size or particle size range. The distribution of particle sizes that make up the abrasives, may be bimodal in nature, according to various exemplary embodiments. Generally speaking, there is a preponderance of two different abrasive particle sizes, or ranges of particle sizes, in the metal polishing slurry.
In other exemplary embodiments, there may not be a continuous distribution of particle sizes but rather only a limited number of discrete particle sizes. In one exemplary embodiment, the abrasives may consist entirely of two particle sizes. In another exemplary embodiment, the two most prevalent particle sizes may constitute 75% of all abrasive particles and in yet another exemplary embodiment, the two most prevalent particle sizes may constitute 90% of all abrasive particles.
The relative populations of the two most prevalent particle sizes will vary in the exemplary embodiments. In
In other exemplary embodiments, the abrasive particles may be characterized by a multimodal distribution of particle sizes, i.e. there may be three or more modes. In some embodiments, the abrasives in the polishing slurry may include a prevalence of three or more different sized particles or three or more different ranges of particle sizes that are most prevalent.
Also disclosed is a method and apparatus for using the polishing slurry in a polishing operation.
The disclosed polishing slurry with a prevalence of two particle sizes produces a generally constant removal rate of the metal or other material being polished. Applicants have discovered that one exemplary embodiment of the disclosed polishing slurry with bimodal particle distribution, produces a generally constant metal removal rate when metal is removed during a CMP operation.
In one aspect, a CMP (chemical mechanical polishing) slurry is provided. The slurry comprises a chemical solution with abrasive particles, the abrasive particles characterized by a multimodal distribution of particle sizes.
A method for chemical mechanical polishing, CMP, is also provided. The method comprises providing a CMP apparatus, disposing a semiconductor substrate in the CMP apparatus, the semiconductor substrate including a metal or other material formed over a substrate surface thereof. The method further comprises introducing a slurry to the CMP apparatus and covering the substrate surface, the slurry comprising a chemical solution with abrasives, the abrasives including a multimodal distribution of particle sizes, and polishing the substrate surface in the CMP apparatus using the slurry.
Also provided is a system for chemical mechanical polishing (CMP) of conductive materials, comprising a CMP apparatus, including a polishing pad with grooves therein and a stage for receiving a semiconductor wafer thereon and in confronting relation with the pad, and a slurry disposed on the pad, the slurry comprising a chemical solution with abrasives, the abrasives including a bimodal distribution of particle sizes.
The preceding merely illustrates the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. For example the disclosed polishing slurry may also be used for polishing other materials used in the manufacture of semiconductor devices.
Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes and to aid in understanding the principles of the disclosure and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.
This description of the exemplary embodiments is intended to be read in connection with the figures of the accompanying drawing, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. The drawings are arbitrarily oriented for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
Although the disclosure has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art without departing from the scope and range of equivalents.
