Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
  • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
  • B24B37/044—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor characterised by the composition of the lapping agent
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/02—Polishing compositions containing abrasives or grinding agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
  • C09K3/1454—Abrasive powders, suspensions and pastes for polishing
  • C09K3/1463—Aqueous liquid suspensions

Definitions

• This invention relates to CMP ("chemical mechanical planarization") materials and specifically to CMP materials for use in treating nickel-phosphorous alloys.
• the specific alloys targeted by the. present invention are known as high-phosphorus alloys and contain 9 to 12 wt% of phosphorous.
• Such alloys are conventionally deposited via an auto catalytic nickel plating process, typically called electroless nickel plating.
• electroless nickel plating Specifically in the manufacture of hard disks for hard-disk-drives (memory storage media) , said nickel-phosphorous alloys are deposited on an aluminum substrate.
• Waviness, roughness, outer diameter curvature and flatness are to be at a minimum in this context.
• Surface defects such as “pits”, “bumps” and “scratches” are defined by any disruption in the nickel-phosphorous lattice, which has a depth or height greater than or equal to twelve angstroms.
• the CMP formulation of this invention is .specifically designed to create a surface on a nickel-phosphorous layer that is suitable in all respects for further operations in the fabrication of a superior electronic component. Specifically it is capable of producing a highly uniform, ' minimum waviness surface in a one-step operation. It does this by using a CMP formulation that- greatly increases the material-removal effectiveness of abrasives with particle sizes more usually associated with the later polishing operation.
• the CMP surface-generating process is accomplished in two operations: a first involving aggressive material removal until an approximate level is achieved and thereafter a more gentl'e process in which the desired surface finish, in terms of' low surface roughness and micro-waviness, is pursued.
• the solutions used in the first polishing stage are frequently comprised of abrasive particles, (usually of alumina) , with a particle size of from about 0.3 to 0.44 micrometers, and a chemical accelerant.
• the second action is a planarization action in which the surface defects created by the first material removal action are removed and a surface with an acceptable pre-determined smoothness and minimal waviness is created.
• This ⁇ second stage of polishing is typically accomplished, using a finer abrasive (colloidal silica) and a chemical accelerant, in the presence of an oxidizer.
• the present invention provides a CMP formulation for "the treatment of a nickel/phosphorus alloy which comprises a dispersion of abrasive particles with particle sizes from 15 to 80 nanometers and selected from the group consisting of silica, alumina, titania, ceria, zirconia and mixtures thereof dispersed in a formulation having a pH of from 2.4 to 2.6 comprising: a. an oxidizer; b. a chemical accelerant comprised of four groups:
• the invention further comprises a single-step process comprising subjecting a nickel-phosphorus alloy containing from 9 to 12% phosphorus deposited on a substrate to a CMP process using a formulation as described above.
• the formulation comprises an organic carboxylic acid. This compound attacks the surface and makes removal of the alloy more easily accomplished.
• suitable acids include citric acid, oxalic acid, lactic acid, tartaric acid, glycine and mixtures of such acids.
• the formulations of the invention are carefully balanced to provide that the attack of the oxidant, (and. any organic carboxylic acid present) , on the nickel- phosphorus alloy surface is not so vigorous that material is removed in uncontrollable amounts that can not be adequately sequestered by the phosphonate group s in the accelerant which is a chelating agent effective to chelate nickel removed from the surface of the nickel-phosphorus alloy and prevent re-deposition, or increase solubility by reacting with ligand providing components in the formulation.
• An important element of the balance is to maintain the pH at the above level and the level of the second accelerant plays an important role in this regard.
• the most preferred example is hydrogen peroxide because of the purity of the product and because it leaves little or no residue.
• oxidants such as periodates, sulphurous acid and percarbamates, can be used in partial or complete substitution for hydrogen peroxide unless there is a compatibility problem as is the case for mixtures of hydrogen peroxide and potassium periodate.
• the preferred oxidant is however hydrogen peroxide and most preferably in the form of a 35% by weight solution in water.
• the moderator for the activity of the oxidant comprises a phosphite or phosphate group having the group - P0 X , where x is from 1 to 4.
• the preferred exemplar is phosphoric acid, (including the- meta-, ortho-, and pyro- phosphoric acid versions) .
• the accelerant also ,comprises chelating phosphonate groups and suitable examples include 1-hydroxyethylidene- 1, 1-diphosphonic acid (HEDP), aminotri (methylenephosphonic acid) (ATMP) , N- (2-hydroxyethyl) -N, N-di
• HEMPA methylenephosphonic acid
• PBTC 2-phosphonobutane- 1,2,4-tricarboxylic acid
• HEDP HEDP
• This component increases the solubility of the nickel removed from the surface and aids in producing a clean surface readily flushed clean of all CMP residues.
• the accelerant also comprises amine, amide or ammonium groups and suitable exemplars of such compounds include ammonium hydroxide, ammonium salts such ammonium nitrate, urea, forma ide acetate, biuret, ethylene diamine and glycine. Mixtures of such compounds can also be used. This compound also acts as a ligand to keep nickel in a soluble form after removal from the surface.
• the amounts of the components in the formulation are preferably as follows:
• Abrasive from 2 to 10 and more preferably from 3 to 6 wt%;
• Oxidizer from 1 to 6 wt% and preferably 1 to 4 wt% of the active oxidant.
• Phosphate or Phosphite from 0.1 to 6 and more preferably from 0.1 to 4 wt%;
• Phosphonate from 0.1 to 6 and more preferably from 0.1 to
• Amine, Amid, Amide or Ammonium from 0.1 to 6 and more preferably from 0.1 to 4 wt%;
• Organic Carboxylic Acid from 0.1 to 6 and more preferably from 0.1 to 4 wt%.
• the most preferred abrasive component of the mixture for use on nickel-phosphorus substrates is silica, having a mean particle size of 15 to 120nm, preferably from 15 to 80nm and most preferably from 15 to 60 nanometers.
• the most suitable silicas have mono-dispersed, essentially spherical particles.
• Two suitable silica solutions are available as 30% by weight solid dispersions.
• A-Green Corp. and DuPont AirProducts NanoMaterials manufacture these products under the trade names BESIL-38A and Syton HD-700 respectively. Of these solutions, Syton HD-700 is preferred.
• the concentration of colloidal silica was held constant at 5.71 percent by weight. This is to -say that in every iteration of slurry, the concentration of colloidal silica by weight .was held constant at 5.71 percent.
• This example illustrates the contribution to removal rate by individual chemical groups in the presence of an oxidizer.
• An initial screening was to be performed involving forty-eight different constituents.
• the concentration of hydrogen peroxide as a thirty-five percent by weight solution was held constant at 2.57. This is to say that during the first phase of the slurry development process hydrogen peroxide in the form of a thirty-five percent by weight solution was held constant in every iteration of slurry at a total percentage by weight of 2.57.
• Each of the remaining forty-seven constituents was evaluated as a one percent by weight solution comprised of silica as described above, hydrogen peroxide as described above, the specific constituent and the remaining weight percent water.
• Table lb shows a myriad of possible constituents as candidates for slurry with adequate removal rate.
• Current state of the art colloidal silica slurries remove the nickel-phosphorous layer at rates from 7mg-12mg per minute per disk, which in comparison to this evaluation would equate to .252g-.432g total removal.
• Table lb shows thirteen slurries which surpass this current bench mark and have, coded units of A6, A17, A19, A20, A23, A27, A29, A30, A31, A32, A41, A43 and A44.
• these constituents are respectively aluminum nitrate, 1- hydroxyethylidene-1, 1-diphosphonic acid (HEDP), sodium fluorophosphate, hydroxyphosphono acetate, phosphoric acid, citric acid, glycine, lactic acid, oxalic acid, tartaric acid, formamid acetate, aminotri (methylenephosphonic acid) (ATMP) and 2-phosphonobutane-l,2, -tricarboxylic acid (PBTC) .
• HEDP 1- hydroxyethylidene-1
• HEDP 1-diphosphonic acid
• ATMP aminotri (methylenephosphonic acid)
• PBTC 2-phosphonobutane-l,2, -tricarboxylic acid
• a ' design of experiment model of resolution fo ⁇ r was utilized where the forty-two slurries were formulated according to table 2a. Further, this table describes the actual percent by weight each constituent was present in a given slurry. This is to say that in the first slurry evaluated, denoted by RunOrder 1, constituents A29, A31, A32 and A5 each were present in concentrations of 1 percent by weight of the total solution while A0 was present in 2.57 percent by weight of the total solution. Silica was held constant as described above at a percent by weight of 5.71 nd the remaining weight percent was water.
• a p-value less than .05 denotes a statistical significance. This is -to say that when a p-value less than .05 is observed, there is sufficient statistical evidence to make inferences about the contribution of an individual constituent or interaction to the system with respect to removal rate.
• Citric Acid HEDP
• Citric Acid Glycine (slightly significant)
• Example 3 illustrates the effects and interactions more specifically of constituents, in coded units, A17, A20, A23, A27 and A29. These constituents in uncoded units are HEDP, HPA, phosphoric acid, ' citric acid and glycine respectively. Again, process procedures, parameters and equipment were held constant as described in tables A and B. Silica was present in each slurry at a concentration of 5.71 percent by weight of the total solution. Hydrogen peroxide in a 35 percent by weight solution was held constant in each slurry at a level of 2.57 percent by weight of the total solution. A fractional factorial design of experiment model was created to incorporate these chemistries.
• Table 3a depicts the levels at which each of the constituents were evaluated.
• slurry number 3 indicated by RunOrder 3, comprised of .1 percent A17, 1.1 percent A27, .1 percent A29, .1 percent A20 and no A23.
• Each of the percentages described above are indicative of a percent by weight of the total slurry.
• the significance of this example is that A29 and A20 are shown to have an adverse effect on removal rate when in the presence of all the other constituents in this specific evaluation. Approximate values of said negative impacts in this specific system are found in table 3b and are characterized by their estimated coefficients,' denoted by "Coef".
• Example 4 Example 4
• Example 4 depicts the effects of individual constituents and interactions of the preferred constituents in this invention.
• these constituents are A0, A17, A23 and A27.
• these constituents in uncoded units are hydrogen peroxide, HEDP, phosphoric acid and citric acid. All procedures, parameters and equipment were held constant as described in tables A and B.
• a fractional factorial design of experiment model was utilized to determine the magnitude of contributions with respect to removaj- rate of each constituent.
• the fractional factorial design of experiment model is portrayed in table 4a.
• Silica was present as 5.71 percent by total weight of each slurry.
• Ammonium hydroxide was utilized to standardize the pH throughout the evaluation at 2.5. Quantitative statistical analysis of the results of this example is available in table 4b. The concentrations of each constituent in each slurry is depicted in table 4a.
• the first slurry evaluated denoted by RunOrder 1, comprised of .25 weight percent A17, .25 weight percent A23, .27 weight percent A27 and 1.29 weight percent A0. Said weight percent values are indicative of total weight percent.
• This example illustrates the performance capability of this invention. All process parameters and equipment were held constant as described in tables A and B when slurry comprising hydrogen peroxide, citric acid, HEDP, phosphoric acid, ammonium hydroxide, silica and water was evaluated. Thirty different runs were performed according to tables A and B. The removal and surface roughness data from these thirty runs were statistically analyzed. Removal rate data is portrayed graphically in table 5a while surface roughness data is portrayed in table 5b. The data acquired from this example depicts a mean removal rate of 18.37mg/min/disk. Accompanying this mean removal rate is a standard deviation of .799mg/min/disk. The surface of the nickel-phosphorous after polishing with this invention is void of defects.
• Defects are . defined as any interruption in the nickel-phosphorous lattice having depth or height greater than twelve angstroms. This is observed through the surface roughness data obtained from this evaluation. A mean surface roughness of 1.47 angstroms was observed with a standard deviation of .17 angstroms. This value of 1.47 angstroms is indicative of the surface condition of the substrate. As measured on a TMS 2000, manufactured by Schmitt Inc., the average difference from peak to valley on the surface of the disks measured was 1.47 angstroms.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Detergent Compositions (AREA)
• Manufacturing Of Magnetic Record Carriers (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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