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Número de publicaciónUS20100059390 A1
Tipo de publicaciónSolicitud
Número de solicitudUS 12/514,142
Número de PCTPCT/US2007/083956
Fecha de publicación11 Mar 2010
Fecha de presentación7 Nov 2007
Fecha de prioridad8 Nov 2006
También publicado comoCN101573212A, WO2008058200A2, WO2008058200A3
Número de publicación12514142, 514142, PCT/2007/83956, PCT/US/2007/083956, PCT/US/2007/83956, PCT/US/7/083956, PCT/US/7/83956, PCT/US2007/083956, PCT/US2007/83956, PCT/US2007083956, PCT/US200783956, PCT/US7/083956, PCT/US7/83956, PCT/US7083956, PCT/US783956, US 2010/0059390 A1, US 2010/059390 A1, US 20100059390 A1, US 20100059390A1, US 2010059390 A1, US 2010059390A1, US-A1-20100059390, US-A1-2010059390, US2010/0059390A1, US2010/059390A1, US20100059390 A1, US20100059390A1, US2010059390 A1, US2010059390A1
InventoresYuzhuo Li
Cesionario originalYuzhuo Li
Exportar citaBiBTeX, EndNote, RefMan
Enlaces externos: USPTO, Cesión de USPTO, Espacenet
METHOD AND APARATUS FOR ELECTROCHEMICAL MECHANICAL POLISHING NiP SUBSTRATES
US 20100059390 A1
Resumen
The present invention relates to an apparatus and a method of electrochemical mechanical polishing (ECMP) for microelectronics applications. The apparatus and method of electrochemical mechanical polishing can be used planarize NiP substrate for a magnetic storage medium and for a process which allows polishing with a controlled surface finish, and a set of corresponding polishing electrolytes and slurry.
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Reclamaciones(14)
1. An electromechanical chemical polishing apparatus for polishing a NiP substrate which comprises:
(a) a fixed carrier body where the NiP substrate is affixed;
(b) a polishing pad below the carrier body and in contact with the NiP substrate, wherein the pad has two layers:
(i) a top layer which is a perforated pad which allows the polishing slurry or electrolyte to have direct contact with the lower layer of the polishing pad; and
(ii) a lower layer which is electrically conductive and acts as a cathode;
(c) an NiP substrate which acts as an anode; and
(d) a power supply.
2. An electromechanical chemical polishing apparatus for polishing a NiP substrate which comprises:
(a) a carrier body where the NiP substrate is affixed;
(b) a first polishing tape which polishes the front side of the NiP substrate;
(c) a second polishing tape which polishes the back side of the NiP substrate;
wherein:
(i) the carrier body with an NiP substrate affixed is rotating between the first and second polishing tape;
(ii) the first and second polishing tape comprise of an electrically conductive material with a thin, porous, non-conductive polymer coating to allow for the first and second tape to carry an slurry or electrolyte;
(d) an an NiP substrate which acts as an anode;
(e) a cathode which is attached to the carrier body; and
(f) a power supply.
3. The apparatus of claim 2, wherein the rotating carrier/NiP substrate moves in a direction which is substantially perpendicular to the movement of the first and second polishing tape.
4. A shear sensitive electrolyte delivery system which is a liposome formed from 5-15% egg lecithin, 25-35% sodium xylenesulfonate and 50-70% deionized water which encapsulated the electrolytes from a 0.2-0.5% solution of CuSO4 which has been added to the liposome.
5. A process of polishing an NiP substrate which comprises affixing an NiP substrate to the apparatus of claim 1 and polishing the substrate with the polishing pad with the addition of a slurry or electrolyte, wherein the surface charge of the substrate is controlled by the electric potential applied onto the surface of the NiP substrate.
6. A process of polishing an NiP substrate which comprises affixing an NiP substrate to the apparatus of claim 2 and polishing the substrate with the first and second tape with the addition of a slurry or electrolyte, wherein the surface charge is controlled by the electric potential applied onto the surface of the NiP substrate.
7. The process of claim 5, wherein the polishing process results in a microwaviness of about 1.0-2.5 (Å/max.amplitude) and a surface roughness of 1.0-2.5 Å.
8. The process of claim 7, wherein the polishing process results in a microwaviness of about 1.0-1.5 (Å/max.amplitude) and a surface roughness of 1.0-1.5 Å.
9. The process of claim 8, wherein the polishing process is a continuous process.
10. The process of claim 9, wherein the electrolyte is delivered by a shear sensitive electrolyte delivery system which is a liposome formed from 5-15% egg lecithin, 25-35% sodium xylenesulfonate and 50-70% deionized water which encapsulated the electrolytes from a 0.2-0.5% solution of CuSO4 which has been added to the liposome
11. The process of claim 6, wherein the polishing process results in a microwaviness of about 1.0-2.5 (Å/max.amplitude) and a surface roughness of 1.0-2.5 Å.
12. The process of claim 11, wherein the polishing process results in a microwaviness of about 1.0-1.5 (Å/max.amplitude) and a surface roughness of 1.0-1.5 Å.
13. The process of claim 12, wherein the polishing process is a continuous process.
14. The process of claim 13, wherein the electrolyte is delivered by a shear sensitive electrolyte delivery system which is a liposome formed from 5-15% egg lecithin, 25-35% sodium xylenesulfonate and 50-70% deionized water which encapsulated the electrolytes from a 0.2-0.5% solution of CuSO4 which has been added to the liposome.
Descripción
    INCORPORATION BY REFERENCE
  • [0001]
    This application claim priority to U.S. Provisional Application 60/846,812, filed on 8 Nov. 2006. Any foregoing applications, and all documents cited therein or during their prosecution (“application cited documents”) and all documents cited or referenced in the application cited documents, and all documents cited or referenced herein (“herein cited documents”), and all documents cited or referenced in herein cited documents, together with any manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention.
  • FIELD OF THE INVENTION
  • [0002]
    The present invention relates to an apparatus and a method of electrochemical mechanical polishing (ECMP) for microelectronics applications. More specifically the apparatus and method of electrochemical mechanical polishing can be used to planarize NiP substrate for a magnetic storage medium and for a process which allows polishing with a controlled surface finish, and a set of corresponding polishing electrolytes and slurry.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Chemical mechanical polishing (CMP—also referred to as chemical mechanical planarization or chemical mechanical etching) has become an essential technology for fabrication of semiconductor devices, magnetic media substrates, and recording head for hard disk drives. See e.g. Chemical-Mechanical Processing (Springer Series in Materials Science), Michael R. Oliver, Springer Publ., (Mar. 24, 2006); Microchip Fabrication, Peter Van Zant, McGraw-Hill (2004); Chemical Mechanical Polishing in Silicon Processing, Volume 63 (Semiconductors and Semimetals), Eds. Shin Hwa Li and Robert O. Miller, Academic Press (1999); Chemical Mechanical Planarization of Microelectronic Materials, Steigerwald et al., John Wiley & Sons (1997).
  • [0004]
    In a typical chemical mechanical polishing (CMP) process, the substrate to be polished is held by a rotating carrier or polishing head, the pad is mounted on a rotating platen or table, and the slurry is delivered into the space between the wafer and the pad. Generally, the substrate, blanket or with patterns, has a thin film of metal, oxide, polysilicon, or other materials. The pad, with grooves and asperities on the surface, brings slurry to be in contact with the wafer and takes removed residues away from the polishing zone.
  • [0005]
    The slurry for CMP typically contains various optional chemical additives such abrasive particles, oxidizer, complexing agent, inhibiting agent, passivating agent, surfactant, and pH adjusting agent.
  • [0006]
    The oxidizer acts to soften the substrate surface. The passivating agent acts to protect the substrate film from chemical attack that may lead to isotropic dissolution. Protection by the passivating agent results in only the substrate materials in the protruded area being selectively removed (thus yielding a step height reduction) by mechanical force via the pad and the abrasive particles held by the pad. Abrasive-free slurries are also known (e.g., U.S. Pat. Nos. 6,800,218 and 6,451,697), in which the abrasive particles are removed. The mechanical action is mainly provided by the polishing pad.
  • [0007]
    The chemical modification of the surface to be polished can be accomplished, instead of an oxidizer, via electrochemical means. In a so-called electrochemical polishing (ECP), the surface to be polished is electrochemically corroded with an electropotential between the conducting substrate and pad serving as electrodes. The material removal from the substrate is mainly accomplished via chemical dissolution. Planarization can be achieved by the differential dissolution rate between the protruded and recessed areas. More specifically, the protruded area often has a slightly higher dissolution rate. In addition to electrochemical modification of the substrate surface, the planarization efficiency can be significantly improved with a direct contact between the substrate and pad.
  • [0008]
    The pad can assist the removal of materials in the protruded area via mechanical action. This method is called electrochemical mechanical polishing (ECMP). Several patents and scientific reports on the use of ECMP approach to planarize silicon wafer substrates have been published, see e.g., U.S. Pat. Nos. 6,977,036; 6,858,531; 6,811,680.
  • [0009]
    These processes and apparatus cited above concern copper CMP and ECMP for the formation of interconnections between active components on a silicon wafer. Although conventional CMP has been applied to the planarization of NiP substrates, use of ECMP has rarely been considered due to the fact that NiP substrates must be polished on both sides simultaneously which does not allow any electrical contact to be made directly on the substrate. The electrical current from both electrodes must be in contact with the NiP substrate locally from the side of a pad.
  • [0010]
    A typical CMP polisher apparatus mainly consists of three parts: the carrier, the platen, and a slurry delivery system. Besides holding the wafer, the carrier also provides the functions of rotating the wafer and adjusting down force & back pressure. The platen rotates the pad to polish the wafer, which, generally, is located below the wafer to be polished. In an orbital CMP polisher, the pad has an orbital motion and thus each point on the pad describes a circle along an orbit. The relative motion between the wafer and the pad is important for a uniform material removal from every point on the wafer surface. Ideally, it is expected to achieve the same or similar velocity for each point on the wafer relative to the pad, which can be realized by maintaining the same or similar rotation speed and the same rotation direction for both the carrier and the platen in rotational polisher.
  • [0011]
    On an ECMP apparatus, the metal film to be polished must be electrically connected and an electro potential must be placed between the surface to be polished and a (conducting) pad. While the design for a conventional CMP slurry must consider the interaction among oxidizer, complexing agent, passivating agent, and abrasive particles, the focus on an electrolyte for ECMP process is on the formation of an effective film on the substrate that allows an effective materials removal in the protruded areas and protection in the recessed areas.
  • [0012]
    In conventional CMP for NiP substrates, in order to reduce processing time, a more mechanically aggressive slurry is used in the first step. This step usually leaves embedded particles and related defects such as scratches. In order to achieve desirable final surface finish, a mechanically soft slurry is applied in the second step. While this second step can usually accomplish the overall planarization needs, many defects still may remain such as nano-asperity caused by the presence of left-over colloidal abrasives and polishing debris. Such nano-asperities sometimes can be removed during the texturing step before the deposition of magnetic materials for longitude magnetic recording devices (LMR).
  • [0013]
    However, with the introduction of perpendicular magnetic recording (PMR), the texturing step is eliminated which poses an even greater challenge to the traditional second step NiP polishing to minimize nano-asperity. ECMP regulates the polishing rate and planarization efficiency through electrochemcial means and combines the two polishing steps in one. Since the polishing debris and nano-asperities are attracted to the NiP via electrostatic charges elimination of the defects can be achieved by modulating the charges of the substrates in an oscillating manner. It will eliminate many particle related defects. In addition, in this invention, a corresponding set of electrolyte will be disclosed which will further reduce the defects commonly seen in a conventional CMP process for NiP substrates.
  • SUMMARY OF THE INVENTION
  • [0014]
    The object of the present invention is to provide an apparatus and a method for electrochemical mechanical polishing (ECMP) of a NiP substrate.
  • [0015]
    This and other objects of the invention are achieved by an apparatus for ECMP which comprises of a polisher, a carrier for NiP substrate, and a uniquely designed pad that is electrically connected to a power supply.
  • [0016]
    Another object of the invention is to provide a method of EMCP of a NiP substrate which comprises of a set of uniquely design electrolytes that enhances the effect of electrical current in step height reduction efficiency and nano-asperity reduction at end.
  • [0017]
    Another object of the invention is to provide a shear sensitive supramolecular structure for the delivery of electrolytes in an EMCP of a NiP substrate.
  • [0018]
    It is noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention.
  • [0019]
    It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless expressly and unequivocally limited to one referent.
  • [0020]
    For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and other parameters used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
  • [0021]
    All numerical ranges herein include all numerical values and ranges of all numerical values within the recited numerical ranges. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
  • [0022]
    All “% by weight” is based on the total weight of the composition, solution or slurry except where otherwise indicated.
  • [0023]
    It is further noted that the invention does not intend to encompass within the scope of the invention any previously disclosed product, process of making the product or method of using the product, which meets the written description and enablement requirements of the USPTO (35 U.S.C. 112, first paragraph) or the EPO (Article 83 of the EPC), such that applicant(s) reserve the right and hereby disclose a disclaimer of any previously described product, method of making the product or process of using the product.
  • [0024]
    The various embodiments and examples of the present invention as presented herein are understood to be illustrative of the present invention and not restrictive thereof and are non-limiting with respect to the scope of the invention.
  • [0025]
    These and other embodiments are disclosed or are apparent from and encompassed by, the following Detailed Description.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0026]
    FIG. 1 depicts a schematic representation of a conventional CMP polisher with a rotary pad and substrate carrier. The slurry is supplied to the pad.
  • [0027]
    FIG. 2 depicts an ECMP polisher for NiP disks in which the substrate to be polished and pad are rotary to the same direction.
  • [0028]
    FIG. 3 depicts the design of a sub-pad that is electrically networked on a plastic circuit board (PCB).
  • [0029]
    FIG. 4 depicts the design of a sub-pad that is electrically networked on a plastic circuit board (PCB) with back electrodes connected to alternating lines.
  • [0030]
    FIG. 5 depicts a typical electrical current locally via an electrolyte.
  • [0031]
    FIG. 6 depicts a local electrical current via an electrolyte and a small portion of the NiP substrate.
  • [0032]
    FIG. 7 depicts the destruction of an ion carrier such as liposome which allows a greater connectivity at the protruded area that leads to greater step height reduction efficiency.
  • [0033]
    FIG. 8 depicts an AFM image of the surface roughness of a NiP substrate polished with a first step slurry of the invention followed by a second step slurry of the invention on an ECMP polisher.
  • [0034]
    FIG. 9 depicts the working principle of a shear or pressure sensitive supramolecular system.
  • [0035]
    FIG. 10 depicts a representative design for a double sided polisher in which the disk to be polished is electrically connected on the side through a holder and via the electrolyte through the holes on the pads.
  • DETAILED DESCRIPTION OF THE INVENTION
  • [0036]
    This invention teaches the use of ECMP approach for the planarization of NiP substrate for applications in computer hard drive magnetic storage media with a set of matching apparatus and electrolytes. In addition to basic performance requirement such as material removal rate, within wafer non-uniformity, surface quality (smoothness, free from scratch, corrosion and pitting spots), the key performance metrics for metal CMP process in the IC (integrated circuit) industry deal with the control of global and local topography at feature level such as dishing, erosion, edge over erosion, etc. While material removal rate is also an important attribute for a NiP CMP process, the key performance requirements are related to the surface finish smoothness and global topography control such as micro waviness and edge roll-off.
  • [0037]
    Unlike the design in a conventional polisher and polishing process, the new design described in this invention places the focus on the electrochemical interaction between the substrate to be polished and the source of mechanical action.
  • [0038]
    The present invention describes the effective and efficient planarization of substrates via an electrochemical mechanical polishing (ECMP) and an apparatus therefore.
  • [0039]
    In one embodiment of the invention, the apparatus for EMCP and the method of EMCP is for a NiP substrate.
  • [0040]
    In one embodiment of the invention, the apparatus for EMCP is shown in FIG. 1 the substrate is fixed onto a carrier, which is located above the polishing pad, wherein the pad has two layers. The top layer is a perforated pad with many holes that allow the polishing slurry or electrolyte to have direct contact with the lower layer. The lower layer is electrically conductive and serves as a cathode. The other electrode is the connected to the back of NiP disk.
  • [0041]
    The EMCP apparatus illustrated in FIG. 1 is an example of a bench top polisher. This design can be scaled up to a floor model (industrial size) by using a much larger platen and pad in the lower portion and placing a larger carrier that can hold multiple disks. Furthermore, the disk carrier can be placed in between two platens that are electrically connected to the cathode. By doing so, both sides of the NiP disks are polished at the same time. For this production level polisher, the electrical connection between the anode and the disks must be on the outer and/or inner rim of the disks. In all cases, the pad must be properly grooved to allow adequate transport of polishing fluid to flow in between the pad and the disks. More importantly, the polishing debris will not accumulate in the pores between the conductive pad and NiP substrate. To proof the concept described in this invention, an ECMP apparatus comprises of a variable speed 12″ grinder-polisher and a power head was constructed. The grinder-polisher is comprised of heavy-duty 1 Hp DC motor, which maintains constant speed under all load conditions, provides variable speeds from 50 to 500 rpm in 10 rpm increments and a digital LED readout that displays wheel speed and a digital LED bar graph for monitoring motor load. Time, force, carrier direction, platen speed and fluid dispensing are microprocessor controlled via and LED display located on the front facia panels of the power head. The time can be varied from 0 to 99 minutes, 59 seconds in 1 second increments. Sample force can be varied from 1 to 60 lbs, in 1 lb. increments with a 1/20 Hp DC motor. The carrier direction can be either clockwise or counterclockwise at a constant speed of 60 rpm. A standard wafer carrier was modified with electrical contacts in order to maintain electrical connection to the NiP surface. In addition, a graphite disc is stacked with a porous pad to provide the electrical contacts as a cathode.
  • [0042]
    An alternative design of the apparatus of the invention is illustrated in FIG. 2. In this particular design, the disk is processed in a rotating carrier which travels through two polishing tapes (front and back). The tape is made of electrically conductive material with a thin polymer coating. The coating should be porous and non-conducting in nature. The conductive portion must be corrosion resistant and flexible. The porosity will allow the tape to carry adequate polishing electrolyte or slurry onto the NiP disk. A significant advantage of this design is the low cost of such polishing tape in relation to the large porous double layer pad shown in FIG. 1. In addition, this design integrated the NiP substrate preparation steps (lapping, polishing, and texturing) and represents a simplification of the polishing process.
  • [0043]
    In a conventional CMP, the surface charge of the film to be polished is mainly dominated by the nature of the oxidizer present in the slurry and the operating pH. However, in an ECMP process, the corresponding surface charge is mainly controlled by the electric potential applied onto the surface. A practical consequence of such difference is the slurry/electrolyte design in which the oxidizer is absent and characteristics of the passivating layer on the surface film to be polished must be strong enough to protect the recessed areas against the flow of slurry or electrolyte yet soft enough to allow effective removal at the protruded areas.
  • [0044]
    A guiding principle for electrolyte design is the use of dissolution/inhibition dual approach. More specifically, complexing agent is added to assist the dissolution of oxidized metal ions and the transport of these ions into the polishing down stream. For the opposite effect, a passivating agent is added to form a protective layer that allows the differential removal of surface materials according to their topographical locations. As a result, a better step height reduction efficiency is achieved. At nanoscale, the step height reduction efficiency can be in part translated to smoothness of finished surface. At micrometer scale, such step height reduction yields a lower microwaviness
  • [0045]
    The two most important attributes for an effective complexing agent are the high formation constant with the metal ions to be removed and the high water solubility of such complex.
  • [0046]
    For an effective passivating agent, the requirement on formation constant is the same. The water solubility of the complex or the solubility of the agent itself in water must be low. As water solubility of many organic substances including their metal complexes are heavily influenced by pH, there is often an optimal pH for a particular pair of complexing and passivating agent. On other hand, one may have to select a specific pair of complexing and passivating agents for a given pH. The oxidization of the metal film is through electrochemical reaction in EMCP, unlike conventional CMP slurry, and therefore, the oxidization process will generally not interfere with the formation of complexing and passivating layers. In addition, an ECMP process has at least one or more of the following advantages over a conventional CMP slurry process:
    • 1. An electrolyte can be formulated at a milder pH range that is not corrosive to the tool and processing equipment.
    • 2. The ECMP process can be conducted at a pH that leads to easier and more effective post CMP cleaning.
    • 3. The ECMP process can polish substrates such as NiP without changing slurries. By way of example, for a CMP process, where NiP is the substrate, a first polishing step is performed with a coarser (first) slurry to remove the bulk amount of surface topography left by the electrochemical deposition process and then subjected to a second polishing step with a finer (second) slurry to achieve the desired surface smoothness and microwaviness. However, for ECMP process, both processes can be conducted continuously using the same slurry. During the first part of the polishing process, the applied electrical current can be adjusted to achieve high removal rate and greater step height reduction efficiency. During the second part of the polishing process, the voltage can be regulated to slow down the polishing to achieve desired surface finish. In the EMCP process, the first part and second part of the polishing process is continuous with no need to change slurries.
  • [0050]
    In one embodiment of the invention, the polishing process results in a microwaviness of about 1.0-2.5 (Å/max.amplitude) and a surface roughness of 1.0-2.5 Å. In another embodiment of the invention, the polishing process results in a microwaviness of about 1.0-1.5 (Å/max.amplitude) and a surface roughness of 1.0-1.5 Å.
  • [0051]
    In another embodiment of the invention, a shear sensitive supramolecular structure for the delivery of electrolytes, which includes but is not limited to a liposomes and cyclodextrins, is used for the ECMP process on NiP substrate. The basic working principle of this supramolecular is illustrated in FIG. 9 which depicts the working principle of a shear or pressure sensitive supramolecular system. Upon shear or stronger down force, the supramolecular structure breaks and release active ingredient into the local polishing region which accelerate the material removal in the protruded area.
  • [0052]
    The supramolecular structure is loaded with electrolytes or ions. The supramolecular structure can be broken and release the encapsulated ions. As the breakage is mainly modulated by shear force, more leakage of ions is expected in the protruded areas on the substrate surface where the asperity is in greater contact with the pad. The release of ions increases the local electrical conductivity. The sudden increase in electrical conductivity leads to an increase in removal in the protruded area. One of the advantages of this system is that the ECMP operation can be simplified into one step as the conductivity and the electrical current is self-regulated in a localized area of the NiP substrate.
  • [0053]
    As the substrate must be planarized on both sides, a polishing scheme must be designed to allow electrochemical reactions to take place on both sides of the NiP disk. FIG. 10 depicts a representative design for a double sided polisher in which the disk to be polished is electrically connected on the side through a holder and via the electrolyte through the holes on the pads.
  • [0054]
    Various combinations of the above embodiments are also within the scope of this invention. The invention will now be further described by way of the following non-limiting examples.
  • Example 1 CMP 1st Step Comparative
  • [0055]
    A slurry is prepared by mixing 2% hydrogen peroxide, 1% lactic acid, and 3% alumina particles (100 nm diameter on average) in water. The slurry was then adjusted to pH=4 using nitric acid or potassium hydroxide. The slurry is then supplied onto the pad of a polisher (Speedfam/IPEC 372 polisher equipped with a modified carrier to hold 95 mm NiP disk) at a flow rate of 100 mL/min. The rotation speed for the pad is 75 rpm and 65 rpm for the carrier/disk. After 3 minutes of polishing, the NiP disk was removed from the carrier and cleaned with DI water and air dried. The material removal rate (MRR) is calculated as the weight loss after polishing using an analytical balance. The surface roughness (Ra) is measured using an AFM (atomic force microscope). The microwaviness was determined on a Zygo 5000 3D optical profilometer. The result is referred as “After 1st Step CMP” in Table 1.
  • Example 2 CMP 2nd Step Comparative
  • [0056]
    The process described in Example 1 was repeated with a slurry prepared by mixing 2% hydrogen peroxide, 1% lactic acid, and 12% colloidal particles (20 nm diameter on average) in water. The result is referred as “After 2nd Step CMP” in Table 1.
  • Example 3
  • [0057]
    The process described in Example 1 was repeated with an electrolyte prepared by mixing 1% lactic acid, 2% sodium phosphate, and 0.1% ammonium nitrate. The result listed in Table 1 is referred as “Using 1st Step ECMP Electrolyte without Electricity.” There is practical no removal of the substrate materials.
  • Example 4
  • [0058]
    The process described in Example 1 was repeated with an electrolyte prepared by using the same electrolyte as described in Example 3. The polishing down force was lowered from 3 psi to 1 psi. The polishing pad was replaced with an ECMP pad. The construction of the pad is illustrated in FIG. 1. As seen in FIG. 1, the cathode and anode of the electrical contacts are both placed behind a porous pad. The electrical circuit is completed with the electrolyte and the NiP substrate. The polishing result listed in Table 1 is referred as “After 1nd ECMP” The electrical current is high for this step. The typical current is 24 mA at 8 Volts.
  • Example 5
  • [0059]
    Similar to Examples 3 and 4, a set of experiments were conducted using the same electrolyte. In this set of experiments, similar to Example 3, the polishing was first conducted using an ECMP electrolyte without electricity at a lower down force. The disk polished in Example 4 was used as the initial starting substrate. The result was referred as “Using 2nd Step ECMP Electrolyte without Electricity.” The removal rate was very low and there is practically no change in the surface microwaviness and roughness.
  • [0060]
    In the second experiment, the polishing was also conducted on a disk which was previously polished using a procedure described in Example 4. The polishing was conducted at 1 psi and low electrical current (12 mA at 4 volts). The result was referred to as “After 2nd step ECMP”. As seen in Table 1, the removal rate is lower than that described in Example 4. The overall surface finish is the best among all disks.
  • Example 6
  • [0061]
    A supramolecular electrolyte, a mixture of 10% egg lecithin, 30% sodium xylenesulfonate and 60% DI water by weight was shaken until a clear micellar phase (L1) was obtained. The micelle phase was diluted with a solution containing 0.4% CuSO4. The mixture was then vigorously stirred for 3 hours. To remove the Cu++ ions located outside of liposome structure, the sample was subject to dialysis using a Molecular/porous membrane tubing obtained from VWR International. The vesicles solution was first diluted 5 times with DI water and placed into the dialysis tube. This dialysis tube was then immersed into 4000 ml of DI water. During the process, the tubes are agitated every 5 minutes to increase sample homogeneity inside of the dialysis tube while the water was constantly stirred. Water was changed 5 times at 1 hour interval. The solution is then ready to use.
  • [0062]
    The polishing result is listed in Table 1 under the “After Single Step ECMP”. An unpolished disk was used in this experiment. As seen in Table 1, the final surface finish is comparable to those experienced two step polishing. One advantage of this approach is high throughput.
  • [0000]
    TABLE 1
    CMP and ECMP polishing of NiP Disks
    Material Removal Microwaviness Surface
    Rate (MRR) (Å/max · Roughness
    (mg/side/min) amplitude) (Ra in Å)
    Before any CMP NA 21 19
    Process
    After 1st Step CMP 50 9 8
    Process
    Using 1st Step ECMP 5 24 24
    Electrolyte w/o
    Electricity
    After 1st Step ECMP 53 2.1 2.4
    process
    After 2nd Step CMP 55 2.7 2.2
    Process
    Using 2nd Step ECMP 2 2.3 2.9
    Electrolyte w/o
    Electricity
    After 2nd Step ECMP 15 1.4 1.1
    After Single Step ECMP 43 1.5 1.2
  • [0063]
    As can be seen from the data, EMCP with electricity outperforms CMP after each of the process steps in terms of microwaviness and surface roughness with an NiP substrate. In addition, the single step EMCP process was able to eliminate a process step while still achieving superior microwaviness and surface roughness with an NiP substrate compared to the CMP process.
  • [0064]
    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims. The scope of the present invention is intended to be defined by the appended claims and equivalents thereto.
Citas de patentes
Patente citada Fecha de presentación Fecha de publicación Solicitante Título
US6250995 *23 Feb 199926 Jun 2001Speedfam Co., Ltd.Apparatus for polishing outer periphery of workpiece
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Clasificaciones
Clasificación de EE.UU.205/674, 204/199, 205/640, 205/686, 204/242
Clasificación internacionalC25F7/00, C25F3/16
Clasificación cooperativaG11B5/8404, B24B37/046, B24B37/20
Clasificación europeaB24B37/20, B24B37/04D, G11B5/84B
Eventos legales
FechaCódigoEventoDescripción
9 Nov 2007ASAssignment
Owner name: ST. LAWRENCE NANOTECHNOLOGY, INC.,NEW YORK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LI, YUZHUO;REEL/FRAME:020090/0401
Effective date: 20071107