# US 6,294,105 B1 · Chemical mechanical polishing slurry and method for polishing metal/oxide layers

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- Number: US 6,294,105 B1
- Document ID: US6294105B1
- Status: Granted
- Kind: B1
- Application number: 08/997,290
- Filed: 1997-12-23
- Granted: 2001-09-25
- Earliest claimed: 1997-12-23
- Assignees: International Business Machines Corporation
- Inventors: Paul M. Feeney; Timothy C. Krywanczyk; Lawrence D. David; Matthew T. Tiersch; Eric J. White
- Web page: https://patentgrep.com/patent/US6294105B1

## CPC

- C09G 1/02: containing abrasives or grinding agents {(abrasives as such C09K3/14; polishing of semi-conductors H10P52/40)}
- C09K 3/1463: {Aqueous liquid suspensions}
- C23F 3/00: Brightening metals by chemical means
- H10P 52/403: {of conductive or resistive materials}
- H10P 95/062: {involving a dielectric removal step}
- C09G: POLISHING COMPOSITIONS (French polish C09F11/00); SKI WAXES
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A ferric nitrate-alumina based slurry useful for Chemical-Mechanical-Polishing of tungsten metallurgy and silica based oxides on semiconductor substrates in which the suspension and stability of abrasive material in the slurry is essentially stable. The slurry formulation is balanced to provide low residue of foreign material after polishing and due to its reduced ferric nitrate concentration will be less corrosive than prior art slurries. The recipe for the slurry includes of a 30% wt silica suspension, about 800 ml of 40% by wt ferric nonahydrate and enough 70% wt nitric acid to adjust the pH of the slurry to about 1.2 to 1.4.

## Claims

### Claim 1

A polishing slurry for CMP applications consisting of
stabilized silica in an aqueous suspension;
an oxidizing agent comprising a metalic ion and an anion, the anion capable of forming soluble salts with metals having Atomic numbers up to 83; and
sufficient quantity of an acid having the same anion as said oxidizing agent to adjust the pH of said slurry to a pH in the range of about 1.2 to 1.4 to maintain said silica in suspension.

### Claim 2 (depends on 1)

The polishing slurry of claim 1 wherein the anion is nitrate.

### Claim 3 (depends on 1)

The polishing slurry of claim 1 wherein the oxidizing agent is ferric nitrate.

### Claim 4 (depends on 3)

The polishing slurry of claim 3 wherein the ferric nitrate is in the form of a nonahydrate.

### Claim 5

The polishing slurry for CMP of metals consisting of:
an aqueous solution containing a suspension of silica;
an oxidizing agent comprising about 800 ml of 40% by weight ferric nitrate hydrate; and
a quantity of 70% by weight nitric acid to provide a pH for the slurry of about 1.2 to 1.4.

### Claim 6 (depends on 5)

The polishing slurry of claim 5 wherein said aqueous solution of stabilized silica is a dispersion of about 30% by weight silica.

### Claim 7

The polishing slurry for tungsten and oxides consisting of:
about 3.75 liters of stabilized silica slurry have about 30% by weight silica;
about 800 ml of 40% by weight of ferric nonahydrate; and
about 25 ml 70% by weight nitric acid.