The disclosure relates generally to chemical-mechanical polishing, and more particularly, to polishing slurries including ceria nanoparticles and methods of chemically-mechanically polishing materials using the same polishing slurries.
Chemical-mechanical polishing (CMP) is a method of removing layers of solid for the purpose of smoothing surfaces and the definition of various layers in the formation of semiconductors or wafers. A primary goal of the CMP process is to polish a surface of the wafer so as to render it both smooth and planar/to have a desired curvature (e.g., non-planar surfaces in lenses). In one example, CMP is a key process in back-end of line integrated circuit (IC) manufacturing. Typically, CMP is carried out using a movable pad and a slurry to polish a surface of a semiconductor or wafer. That is, in conventional CMP processes a first slurry having a large particle size and large abrasion coefficients are used to remove material. This process results in a quick removal of material, but leaves the surface rough and non-planar. To smooth and planarize the surface, a second slurry including small particle sizes and lower abrasion coefficients is used to remove the rough material, and smooth/planarize the surface.
The conventional two-part polishing process takes a significant amount of time to complete—which is especially attributed to the second step using the small particle size slurry. Furthermore, conventional CMP processes and techniques, while smoothing and mostly planarizing a surface, result in other negative effects and/or build consequences within the semiconductors or wafers. For example, dishing (see,
A first aspect of the disclosure provides a polishing slurry. The polishing slurry includes: colloidal ceria nanoparticles having at least 20% surface concentration of Ce3+ oxidation state cerium atoms.
A second aspect of the disclosure provides a method for polishing a material. The method includes: continuously flowing a slurry over a surface of the material, the slurry including: deionized water, colloidal ceria nanoparticles having at least 20% surface concentration of Ce3+ oxidation state cerium atoms, the colloidal ceria nanoparticles include a concentration having a range of 0.01 wt. % to 3.0 wt. %, and hydrogen peroxide including a concentration having a range of 0.015 wt. % to 1.5 wt. %; and chemically and mechanically removing a portion of the material, the portion including the surface of the material exposed to the slurry.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
As an initial matter, in order to clearly describe the current disclosure it will become necessary to select certain terminology when referring to and describing relevant machine components within the disclosure. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.
As discussed herein, the disclosure relates generally to chemical-mechanical polishing, and more particularly, to polishing slurries including ceria nanoparticles and methods of chemically-mechanically polishing materials using the same polishing slurries.
These and other embodiments are discussed below with reference to
Ceria 102 included within polishing slurry 100 may include and/or may be formed as a plurality of ceria nanoparticles 108. As shown in the enlarged or magnified portion “A” of polishing slurry 100, ceria nanoparticles 108 maybe colloidal, and/or polishing slurry 100 may include a colloidal dispersion of ceria nanoparticles 108 therein. Ceria nanoparticles 108 of polishing slurry 100 may including or be formed as, for example, an oxide form of elemental cerium (Ce), and may have a predetermined and/or desired surface concentration of Ce3+ and Ce4+ oxidation state cerium atoms. In a non-limiting example, ceria nanoparticles 108 may have at least a 20% surface concentration of Ce3+ oxidation state cerium atoms, and more specifically a range of surface concentration of Ce3+ oxidation state cerium atoms between approximately 20% and approximately 35%. As discussed herein, the surface concentration of Ce3+ oxidation state cerium atoms may be dependent at least in part on the size or dimension of ceria nanoparticles 108 and/or a concentration of hydrogen peroxide (H2O2) 106 present in polishing slurry 100. Additionally, and as discussed herein, the surface concentration of Ce3+ oxidation state cerium atoms for each ceria nanoparticle 108 may affect a chemical reaction between polishing slurry 100 and a material to be polished using a chemical-mechanical polishing process.
Ceria nanoparticles 108 of ceria 102 may also include a predetermined and/or predefined dimension or size (S). In one non-limiting example, colloidal ceria nanoparticles 108 may include a size (S) range of between approximately 5 nanometers (nm) and approximately 100 (nm). In this example, the size (S1, S2) of ceria nanoparticles 108 may be substantially uniform within polishing slurry 100. In another non-limiting example, colloidal ceria nanoparticles 108 may include a bimodal size distribution. The bimodal size distribution for ceria nanoparticles 108 may be separated by approximately 20 nanometers (nm), such that the bimodal size distribution for ceria nanoparticles 108 ranges between approximately 25 nanometers and approximately 45 nanometers (e.g., S1), and between approximately 80 nanometers and approximately 100 nanometers (e.g., S2), respectively. In a further non-limiting example, the colloidal ceria nanoparticles 108 may include a multimodal size distribution separated by approximately 20 nanometers. The multimodal size distribution for ceria nanoparticles 108 may range, for example, between approximately 5 nanometers and approximately 25 nanometers (e.g., S1), between approximately 40 nanometers and approximately 60 nanometers (e.g., S2), and between approximately 75 nanometers and 95 nanometers (e.g., S3), respectively. The dimension or size (S) of ceria nanoparticles 108 of ceria 102 may determine, impact, and/or influence the surface concentration of Ce3+ oxidation state cerium atoms included therein. For example, smaller ceria nanoparticles 108 (e.g., S=5 nm) may include a larger surface concentration of Ce3+ oxidation state cerium atoms, than larger ceria nanoparticles 108 (e.g., S=65 nm). In this non-limiting example larger ceria nanoparticles 108 (e.g., S=65 nm) may have a larger surface concentration of Ce4+ oxidation state cerium atoms. As discussed herein, additional material, elements, and/or additives may be added to polishing slurry 100 to interact/react with ceria nanoparticles 108 to increase the surface concentration of Ce3+ oxidation state cerium atoms in ceria nanoparticles 108.
Ceria 102, and more specifically ceria nanoparticles 108, includes a predetermined and/or predefined concentration weight percent (wt. %) of polishing slurry 100. In a non-limiting example, colloidal ceria nanoparticles 108 may include a concentration within a range of approximately 0.01 wt. % to approximately 3.0%. As discussed herein, the predetermined concentration of ceria nanoparticles 108 may aid and/or improve the chemical-mechanical polishing process performed on a material by reducing polishing time, improving a surface finish (e.g., smoothness, planarization characteristics), and/or reducing the amount of ceria 102 required in polishing slurry 100. The reduced amount of ceria 102 in polishing slurry 100 may ultimately reducing the cost of polishing slurry 100 and/or the amount of polishing slurry 100 required to perform the polishing process.
As shown in
The concentration of hydrogen peroxide (H2O2) 106 may be dependent upon, at least in part, the dimension or size (S) of ceria nanoparticles 108, the concentration weight percentage of ceria nanoparticles 108, and/or the surface concentration of Ce3+ oxidation state cerium atoms in ceria nanoparticles 108. In a non-limiting example, the concentration weight percentage (wt. %) of hydrogen peroxide (H2O2) 106 may be less than the concentration weight percentage (wt. %) of ceria nanoparticles 108 within polishing slurry 100. More specifically, polishing slurry 100 may include a 2:1 ratio or relationship between the weight percentage of ceria nanoparticles 108 and hydrogen peroxide (H2O2) 106. In this example, colloidal ceria nanoparticles 108 may include a concentration of approximately 1.0 wt. %, while hydrogen peroxide (H2O2) 106 includes a concentration of approximately 0.5 wt. %. In other non-limiting examples, the concentration weight percentage (wt. %) of hydrogen peroxide (H2O2) 106 may be substantially equal to or greater than the concentration weight percentage (wt. %) of ceria nanoparticles 108 within polishing slurry 100. The addition of hydrogen peroxide (H2O2) 106 to polishing slurry 100 may increase the surface concentration of Ce3+ oxidation state cerium atoms in ceria nanoparticles 108. That is, adding hydrogen peroxide (H2O2) 106 to polishing slurry 100 may result in a reaction with, and more specifically a decomposition by, ceria nanoparticles 108, similar to the action of, for example, the enzyme catalase. When the initial percentage of Ce3+ on the particle surface is low, this reaction increases the surface concentration of Ce3+ oxidation state cerium atoms in ceria nanoparticles 108 from the base and/or unreacted surface concentration of Ce3+ oxidation state cerium atoms for ceria 102. When the initial percentage of Ce3+ on the particle surface is high, the addition and decomposition of hydrogen peroxide (H2O2) 106 decreases the surface concentration of Ce3+ oxidation state cerium atoms in ceria nanoparticles 108, resulting in an increase in the percentage of Ce3+ oxidation state cerium atoms for ceria 102. As discussed herein, controlling the surface concentration of Ce3+ oxidation state cerium atoms for nanoparticles 108 in polishing slurry 100 may aid in and/or improve a chemical reaction (e.g., condensation reaction) between polishing slurry 100 and the material being chemically-mechanically polished using polishing slurry 100.
Polishing slurry 100 may also include a buffer material 110. Buffer material 110 may be added and/or included in polishing slurry 100 to adjust the pH of polishing slurry 100. More specifically, buffer material 110 may be added, included, and/or formed in polishing slurry 100 to adjust or alter the pH of polishing slurry 100 to a desired or predetermined pH. The desired or predetermined pH level of polishing slurry 100 may be dependent, at least in part, on the composition or make-up of the material undergoing the chemical-mechanical polishing process using polishing slurry 100. The pH level of polishing slurry 100, as determined or adjusted by, at least in part, buffer material 110, may be within a range of approximately pH 1 to approximately pH 12. In a non-limiting example, buffer material 110 may be added to polishing slurry 100 to adjust the pH to between approximately pH 8 and pH 10 when polishing slurry 100 is used to polish a material including copper, cobalt, ruthenium, and/or any other metal or metal-alloy material including similar material/mechanical characteristics (e.g., hardness, ductility, strength, elasticity, isoelectric point etc.). In another non-limiting example, buffer material 110 may be added to polishing slurry 100 to adjust the pH to between approximately pH 6 and pH 8 when polishing slurry 100 is used to polish a material including silicon, and/or quartz, and/or any other silica/polymer material (e.g., SiO2, soda glass, borosilicate, other silica-based glasses) including similar material/mechanical characteristics. In a further non-limiting example, buffer material 110 may be added to polishing slurry 100 to adjust the pH to between approximately pH 1 and pH 2 when polishing slurry 100 is used to polish a material including tungsten and/or any other metal or metal-alloy material including similar material/mechanical characteristics. Still further, the pH of polishing slurry 100 may be adjusted similarly as discussed herein to polish other materials including, but not limited to, manufactured sapphire or other planar-crystalline material, gemstones, and/or naturally occurring materials that may require/undergo a polishing technique prior to use.
The pH level of polishing slurry 100 may be determined by the amount or concentration weight percentage (wt. %) of buffer material 110 added therein and/or the composition or type of buffer material 110 added to polishing slurry 100. In non-limiting examples, buffer material 110 added to polishing slurry 100 may include, but is not limited to, Potassium hydroxide (KOH), sodium hydroxide (NaOH); nitric acid (HNO3), nitrite (NO2−), sulfate (SO42−), phosphate (PO43−), ammonia (NH3) or ammonium hydroxide (NH4OH), and/or other suitable materials including similar material/reactive characteristics. As discussed herein, adjusting the pH of polishing slurry 100 may affect (e.g., improve) the rate of condensation reaction between ceria nanoparticles 108 in polishing slurry 100 and the material being polished by polishing slurry 100.
In the non-limiting example shown in
Polishing slurry 100, as shown in
Although shown in
Turning to
Polishing system 118 may include wafer carrier 120. Wafer carrier 120 may hold and/or move wafer 10 during the polishing process as discussed herein. As shown in
In the non-limiting example where material 20 is formed from copper (Cu), oxidized portion 24 formed via a redox reaction may be formed as copper oxide (Cu2O or CuO), while the remainder of first layer 18 may remain copper (Cu). The penetration depth or thickness (T) of oxide portion 24 formed in first layer 18 may be predetermined and/or calculated based on a variety of operational parameters and/or characteristics. For example, and as discussed herein, the thickness (T) of oxide portion 24 may be dependent, at least in part on, the concentration of hydrogen peroxide (H2O2) 106 within polishing slurry 100, the pH of polishing slurry 100 flowing over surface 22 of material 20 for wafer 10, and/or exposure time. Additionally, during the polishing process the reduction of thickness (T) of oxide portion 24 formed in first layer 18 for wafer 10 is dependent on the size (S) and concentration of ceria nanoparticles 108 included within polishing slurry 100, applied force/pressure to wafer 10 into polishing slurry 100, and/or movement characteristics of carrier 120/platen 122 (e.g., direction of movement, speed, vibration, etc.).
Oxidized portion 24 of first layer 18 formed from material 20 may be removed using one of, or a combination of, chemical and/or mechanical reactions/responses. For example, at least a section of oxidized portion 24 may be removed from first layer 18 via a chemical reaction within oxidized material 20. That is, and based on the exposure to ceria nanoparticles 108 of polishing slurry 100 and the resulting condensation reaction occurring therebetween, at least a section of oxidized portion 24 may, break down, and/or be removed from the remainder of oxidized portion 24 and/or the remaining portion of first layer 18. Additionally, or alternatively, oxidized portion 24 (or the remaining section of oxidized portion 24) may be mechanically abraded away from the remainder of material 20 forming first layer 18 of wafer 10. That is, the abrasive properties of ceria nanoparticles 108 of polishing slurry 100, as well as the operational characteristics/parameters of polishing system 118 (e.g., movement of carrier 120 and/or polishing pad 124, pressure of wafer 10 against polishing slurry 100) may result in the abrading, eroding, and/or removal of oxidized portion 24 from the remainder of first layer 18 of wafer 10. In addition to the removal of oxidized portion 24, the abrasive properties of ceria nanoparticles 108 of polishing slurry 100, as well as the operational characteristics/parameters of polishing system 118 may result in the formation of polished surface 26 in first layer 18 of wafer 10.
Although shown as forming oxidized portion 24 in
In process P1, a pH and/or a composition of the polishing slurry may be predetermined. That is, a pH of the polishing slurry used by a polishing system to chemically-mechanically polish a material may be predetermined, predefined, and/or precalculated. The predetermined pH may be dependent or based on a composition of the material being polished using the polishing slurry. Predetermining the pH of the polishing slurry may also include ensuring and/or (compositionally) modifying the polishing slurry such that the actual pH of the slurry matches the predetermined pH. The pH of the polishing slurry may be modified, for example, using a buffer material.
Additionally, or alternatively, a composition of the polishing slurry used by a polishing system to chemically-mechanically polish a material may be predetermined, predefined, and/or analyzed. Similar to the pH, the composition of the polishing slurry may be dependent or based on a composition of the material being polished using the polishing slurry. That is, the composition of the polishing slurry may be predetermined and/or analyzed based on the material to be polished to determine if additional materials, elements, particles, and/or additives (e.g., supplemental additives) should be added to the polishing slurry prior to the flowing (e.g., process P2). In response to determining that the polishing slurry does not include the composition desired and/or required to polish the material, predetermining the composition of the polishing slurry may also include modifying the polishing slurry such that the composition of the slurry matches the predetermined, desired, and/or required composition. For example, where copper is the material to be polished, supplemental additives may be added to the polishing slurry to aid in the chemically-mechanically polish (e.g., process P3) the copper as desired.
In process P2 polishing slurry may be flowed over a surface of the material being polished. More specifically, polishing slurry may be continuously flowed over the surface of the material undergoing the chemical-mechanical polish. The polishing slurry may include the predetermined pH that is based on the material. Additionally, the polishing slurry may include deionized water and colloidal ceria nanoparticles. In a non-limiting example, the ceria nanoparticles of the polishing slurry may have at least 20% surface concentration of Ce3+ oxidation state cerium atoms. Additionally, the colloidal ceria nanoparticles may include a concentration having a range of 0.01 wt. % to 3.0 wt. %. Finally, the polishing slurry may also include hydrogen peroxide (H2O2) including a concentration having a range of 0.015 wt. % to 1.5 wt. %.
In process P3, a portion of the material may be chemically and mechanically removed. The portion chemically and mechanically removed may include the surface of the material exposed to the polishing slurry. In a non-limiting example, the chemical and mechanical removal of the portion of the material may also include the oxidation of the surface of the material in response to continuously flowing the polishing slurry over the surface of the material, and subsequently causing or creating a condensation reaction between the newly formed or existing oxidized surface of the material and the ceria nanoparticles, resulting in material attaching to the surface of the ceria nanoparticles and detaching from the surface being polished. That is, and as a result of the size of the ceria nanoparticles, the surface concentration of Ce3+ oxidation state ceria atom for the ceria nanoparticles, the presence of the hydrogen peroxide (H2O2) in the polishing slurry, and/or the pH of the polishing slurry, a condensation reaction between the polishing slurry and the material may take place, and result in a portion of the material being removed from the surface. In the non-limiting example, the chemical and mechanical removal of the portion of the material may further include (chemically) breaking down, and/or removing the oxidized portion from the remainder of the material, and/or abrading, eroding, and/or removing the oxidized portion from the remainder of the material. Furthermore, chemically and mechanically removing the (oxidized) portion may also include forming a smooth, polished surface on the material.
By comparison,
By comparison,
In addition to the operational/manufacturing improvements shown and discussed herein, the use of polishing slurry 100 discussed herein with respect to
The foregoing drawings show some of the processing associated according to several embodiments of this disclosure. In this regard, each drawing or block within a flow diagram of the drawings represents a process associated with embodiments of the method described. It should also be noted that in some alternative implementations, the acts noted in the drawings or blocks may occur out of the order noted in the figure or, for example, may in fact be executed substantially concurrently or in the reverse order, depending upon the act involved. Also, one of ordinary skill in the art will recognize that additional blocks that describe the processing may be added.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately” as applied to a particular value of a range applies to both values, and unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
This application claims the benefit of U.S. Provisional Application No. 62/914,540, filed Oct. 13, 2019, and U.S. Provisional Application No. 62/955,047, filed Dec. 30, 2019—both of which are hereby incorporated herein by reference.
Number | Date | Country | |
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62914540 | Oct 2019 | US | |
62955047 | Dec 2019 | US |