# US 9,437,442 B2 · Methods for polishing phase change materials

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- Number: US 9,437,442 B2
- Document ID: US9437442B2
- Status: Granted
- Kind: B2
- Application number: 13/924,790
- Filed: 2013-06-24
- Published: 2013-11-07
- Granted: 2016-09-06
- Earliest claimed: 2007-02-14
- Assignees: Micron Technology, Inc.
- Applicants: Micron Technology, Inc.
- Inventors: Zhenyu Lu; Jun Liu
- Web page: https://patentgrep.com/patent/US9437442B2

## CPC

- H10P 52/402: {of semiconductor materials}
- C09G 1/02: containing abrasives or grinding agents {(abrasives as such C09K3/14; polishing of semi-conductors H10P52/40)}
- C09K 3/1409: {Abrasive particles per se (preparation of diamond C01B32/25)}
- C09K 3/1463: {Aqueous liquid suspensions}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- C09G: POLISHING COMPOSITIONS (French polish C09F11/00); SKI WAXES
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A slurry for polishing a phase change material, such as Ge—Sb—Te, or germanium-antimony-tellurium (GST), includes abrasive particles of sizes that minimize at least one of damage to (e.g., scratching of) a polished surface of phase change material, an amount of force to be applied during polishing, and a static etch rate of the phase change material, while optionally providing selectivity for the phase change material over adjacent dielectric materials. A polishing method includes applying a slurry with one or more of the above-noted properties to a phase change material, as well as bringing the polishing pad into frictional contact with the phase change material. Polishing systems are disclosed that include a plurality of sources of solids (e.g., abrasive particles) and provide for selectivity in the solids that are applied to a substrate or polishing pad.

## Claims

### Claim 1

A method for polishing a phase change material, comprising:
applying a slurry to at least one of a polishing pad and the phase change material, the slurry consisting essentially of:
from about 1% by weight to about 2% by weight of a peroxide;
from about 0.01% by weight to about 0.05% by weight of ammonium citrate; and
from about 500 ppm to about 1000 ppm of benzotriazole; and
from about 1% by weight to about 2% by weight colloidal silica particles, each having a particle size of about 30 nm or less; and
polishing the phase change material with the polishing pad.

### Claim 2 (depends on 1)

The method of claim 1, wherein applying a slurry to at least one of a polishing pad and the phase change material comprises:
supplying the peroxide, the ammonium citrate, and the benzotriazole of the slurry to the at least one of the polishing pad and the phase change material using a first applicator; and
supplying the colloidal silica abrasive particles of the slurry to the at least one of the polishing pad and the phase change material using a second applicator.

### Claim 3 (depends on 1)

The method of claim 1, further comprising mixing the peroxide, the ammonium citrate, the benzotriazole, and the colloidal silica abrasive particles before applying the slurry to the at least one of the polishing pad and the phase change material.

### Claim 4 (depends on 1)

The method of claim 1, further comprising diluting the slurry on the at least one of a polishing pad and the phase change material.

### Claim 5 (depends on 1)

The method of claim 1, wherein polishing the phase change material with the polishing pad comprises bringing the polishing pad into frictional contact with the phase change material using an applied downforce of less than or equal to about 3.0 psi.

### Claim 6 (depends on 1)

The method of claim 1, wherein polishing the phase change material with the polishing pad comprises bringing the polishing pad into frictional contact with the phase change material using at least two different applied downforces.

### Claim 7 (depends on 6)

The method of claim 6, wherein bringing the polishing pad into frictional contact with the phase change material using at least two different applied downforces comprises:
removing a portion of the phase change material using an initial applied downforce; and
removing another portion of the phase change material using another applied downforce, the another applied downforce less than the initial applied downforce.