Abrading – Abrading process
Reexamination Certificate
1999-10-22
2002-02-19
Rachuba, M. (Department: 3724)
Abrading
Abrading process
C451S060000, C051S307000, C051S308000, C051S309000, C438S693000
Reexamination Certificate
active
06347978
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns polishing compositions and methods for using the polishing compositions to polish rigid disks. The compositions generally include colloidal silica and at least one hydroxylamine polishing additive. More particularly the compositions and method of this invention are adapted for polishing electroless nickel deposited rigid disks that are used in computer hard drives.
2. Description of the Related Art
There exists a continuing desire to miniaturize electronic components used in the computer and electronics industries. The driving force for miniaturization in rigid disks is similar to that in the semiconductor industry. Customers are demanding continually increasing storage capacity in rigid disks. At the same time the design rules used by computer manufacturers call for smaller hard drives. The only solution available to rigid disk manufacturers is to increase the storage density of the magnetic media.
Miniaturization has created component quality concerns, many of which are resolved by the precise polishing of computer and electronic substrate materials for magnetic disks and semiconductors. As a result, identifying methods and compositions that can produce an essentially defect free electronic substrate surface has become crucial in the manufacture of smaller and smaller computer and electronic substrates.
Dispersions and chemical mechanical polishing (CMP) slurries have been developed for use in conjunction with semiconductor device manufacture. However, few of the commercially available dispersions or CMP slurries have been evaluated in rigid disk polishing applications. For example, U.S. Pat. No. 4,475,981 discloses polishing the metal surface of nickel plated blanks for rigid memory disks with a composition including ceric oxide or aluminum oxide powder, a water soluble chlorine-containing mild oxidizing agent and an aqueous suspension of colloidal alumina oxide or ceria oxide. U.S. Pat. Nos. 4,696,697 and 4,769,046, each disclose methods for polishing memory disks using an abrasive composition including alpha-aluminum oxide and a polishing accelerator such as nickel sulfate. The aluminum oxide polishing agent preferably has a minum particle size of 0.7-4 &mgr;m and a maximum particle size of 20 &mgr;m or less. U.S. Pat. Nos. 4,915,710 and 4,929,257 each disclose abrasive compositions suitable for polishing aluminum based substrates for magnetic recording disks. The composition disclosed includes an alumina abrasive, a polishing accelerator such as gluconic or lactic acid and colloidal alumina. In addition, U.S. Pat. No. 5,527,423 discloses an abrasive composition that is particularly useful in the method of this invention. Likewise, U.S. patent application Ser. No. 08/753,482, incorporated herein by reference, discloses a chemical mechanical abrasive composition including an oxidizer and a catalyst that is useful in the method of this invention. Polishing compositions including an alumina abrasive and a hydroxylamine additive are disclosed in U.S. Pat. No. 5,735,963.
Methods for polishing rigid disks are disclosed in U.S. Pat. Nos. 4,769,046, 5,084,071, and 5,441,788 each of which are incorporated herein by reference. U.S. Pat. No. 4,769,046 discloses a method for polishing a layer of nickel plated on a rigid disk using a composition comprising aluminum oxide and a polishing accelerator such as nickel nitrate, aluminum nitrate, or mixtures thereof. U.S. Pat. No. 5,084,071 discloses a method of chemical mechanical polishing and electronic component using a composition including abrasive particles that are not alumina, a transition metal chelated salt, a solvent for the salt, and a small but effective amount of alumina. Finally, U.S. Pat. No. 5,441,788 discloses a method for manufacturing a nickel phosphor recording disk including polishing the NiP substrate to a surface roughness to no less than 2.0 nm RMS.
Commercially available rigid disk polishing slurries are unable to meet the new rigid disk surface finish parameters. Furthermore, compositions that are presently known to be capable of polishing rigid disks are unable to polish rigid disks at a high rate and, at the same time, produce an acceptable surface finish. Therefore, there remains a need for polishing compositions that are capable of polishing rigid or hard disks at high rates with low defectivity, while providing a smooth surface finish.
SUMMARY OF THE INVENTION
The present invention is directed to compositions that are capable of polishing rigid disks at high rates with little or no increase in disk defectivity.
The present invention is also directed to compositions that are useful in conjunction with an abrasive polishing pad and/or in conjunction with a particulate abrasive for polishing electronic substrates.
The present invention is further directed to a method for removing nickel phosphide from an aluminum alloy-based rigid disk at high rates with polishing compositions.
In one embodiment, this invention is a polishing composition comprising water and at least one hydroxylamine additive wherein the polishing composition is combined with aqueous colloidal silica to give a polishing slurry or wherein the colloidal silica is embedded or applied to a polishing pad and thereafter the polishing composition is combined with the abrasive pad.
In still another embodiment, this invention is a method for polishing a rigid disk. The method includes the steps of: (a) providing a polishing composition comprising water and at least one hydroxylamine additive; (b) applying the polishing composition to at least one surface of the rigid disk; and (c) removing at least a portion of a metal layer from the rigid disk by bringing a polishing pad into contact with the surface of the rigid disk and moving the pad in relation to the rigid disk to give a polished rigid disk where colloidal silica is incorporated into the polishing composition, the polishing pad or both.
DESCRIPTION OF THE CURRENT EMBODIMENT
The present invention relates to polishing compositions of matter useful for polishing rigid disks. The present invention also relates to a method for polishing rigid disks using a polishing composition with specific additives including colloidal silica and hydroxylamine. In particular, the polishing composition of the invention are capable of polishing rigid disks at good rates to give polished rigid disks having excellent RMS roughness of less than about 0.6 nm at polishing rates greater than about 1.5&mgr; inch/min/side.
Before describing the details of the various preferred embodiments of this invention, terms that are used herein will be defined. The term “rigid disk” refers to rigid disks and hard disks, such as an aluminum disk or nickel phosphor (NiP) plated aluminum disk upon which a magnetic media for computer memories will be coated.
An aspect of this invention is a method for polishing rigid disks that uses a polishing composition that has heretofore been unappreciated as being useful for polishing rigid disks. Polishing compositions useful for polishing rigid disks according to this invention include at least one hydroxylamine additive and colloidal silica. The polishing compositions of this invention may be combined with colloidal silica in a slurry to give a polishing composition that is useful for polishing rigid disks or the colloidal silica may be incorporated into a polishing pad and thereafter combined with an aqueous hydroxylamine solution. Examples of abrasive pads useful with polishing compositions of this invention are disclosed in U.S. Pat. Nos. 5,849,051 and 5,849,052 which are incorporated herein by reference.
The polishing compositions of this invention include at least one hydroxylamine additive. The term hydroxylamine additive as used herein refers to hydroxylamine (NH
2
OH), derivatives of hydroxylamine, and hydroxylamine salts including, for example, nitrate salts, sulfate salts, phosphate salts and mixtures thereof. U.S. Pat. No. 5,735,963, the specification of which is incorporated herein by reference, discloses hydr
Fang Mingming
Streinz Christopher C.
Wang Shumin
Cabot Microelectronics Corporation
Rachuba M.
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