CMP Slurry PROCESS MATERIALS REFERENCE
Material / application dossier

Tungsten CMP Slurry: Selectivity, Recess & Control

Tungsten CMP must clear the field while preserving tungsten in the intended features and controlling loss of surrounding films. Surface reaction, removal and chemical loss need separate measurements.

Sources reviewed Evidence & limits
WPROCESS DOSSIER
Target material
Tungsten overburden
Process role
Contact / via fill clearing
Primary objective
Clear fields while limiting feature recess
Important chemistry
Oxidation and particle-mediated removal
Performance variables
W / dielectric rates, static loss, endpoint
Common failure modes
Recess, residual W, scratches, oxide loss
Selectivity concerns
W removal relative to adjacent dielectric, with patterned feature recess assessed separately.
Conceptual Tungsten overburden process cross-section
Conceptual film balance; not to scale or a production specification.

Start with the tungsten integration scheme

Tungsten is used in semiconductor contact and plug structures, among other applications. Specify the deposited film, liner or barrier, surrounding dielectric and clearing objective rather than assuming all tungsten steps have the same rate balance.

A bulk step, a selective clearing step and a buff can require different products. Entegris’s current brochure describes selective, nonselective and buff offerings within its tungsten portfolio. These are supplier-defined options, not evidence that one family is suitable for a particular fab. Disclosed tungsten portfolio ↗

Oxidation does not mean uncontrolled dissolution

In published tungsten mechanisms, oxidizing chemistry produces a modified oxide-containing surface; contact can remove that layer while the reaction layer can also restrict attack of underlying metal. The behavior depends on the liquid and conditions. Tungsten mechanism overview ↗

A study on tungsten dissolution suppression examines coordination chemistry in an oxidizing system. Its result supports treating dissolution and polishing removal as distinct responses; it does not define an appropriate additive or concentration for another process. Tungsten dissolution study ↗

Selectivity and feature recess

ConcernEvidence to requestQualification implication
Tungsten / dielectric balanceRates for the exact surrounding film, measured under matched conditions.A nominal “W-to-oxide ratio” is incomplete if the integration uses a different film.
Liner / barrier exposureRemoval and chemical-loss data for each exposed layer.Clearing tungsten does not prove acceptable liner removal.
Feature recessPatterned profiles over feature size and overpolish.Blanket selectivity cannot predict retained feature height on its own.
Residual field tungstenEndpoint and clearing data across the wafer.A protective product can still leave incomplete clearing.
Surface qualityRoughness, scratches, pits and after-clean contamination.Separate mechanical defects from chemical loss and residues.
Point-of-use agingResults over the documented preparation-to-use interval.A stable supplied product need not have the same use-life after activation.

Abrasive and preparation questions

Silica and alumina are discussed in tungsten CMP literature. Do not derive current product suitability from the abrasive alone. Ask the supplier which particle specification applies to the product and how distribution-tail control is maintained through storage, dilution and delivery.

  • Identify whether an oxidizer or activator is supplied separately.
  • Confirm preparation order and how prepared material is identified and timed.
  • Define allowable point-of-use concentration and the measurement used to control it.
  • Review filter compatibility with the actual product, including initial conditioning.
  • Agree how residue is measured after the intended clean and how re-deposition is assessed.

Release criteria should reflect the feature

Use separate gates for field clearing, recess, adjacent-film loss and after-clean surface quality. A candidate can pass average rate and fail any of these. Include both center-to-edge behavior and the feature populations that determine device risk.

Record the pad-life range, lots, tools and queue conditions covered by the qualification. If a supplier offers a modified version of the product, compare it against those same gates rather than accepting a statement that the chemistry is “equivalent.”

Sources & evidence

  1. Suppression of Dissolution Rate via Coordination Complex in Tungsten CMP ↗Peer-reviewed research · Applied Sciences · 2022. Oxidation and dissolution control in the reported tungsten system. Indexed publisher excerpts reviewed; direct retrieval rate-limited.
  2. Abrasive for Chemical Mechanical Polishing ↗Technical chapter · IntechOpen · 2018. Abrasive roles in metal and dielectric CMP, including tungsten surface oxidation. Historical application statements should not be read as current market facts.
  3. Entegris — Synergies to Improve CMP Yield brochure ↗Manufacturer brochure · 2026. Disclosed EPOCH, i-Cue, Sentinel, WIN, Semi-Sperse, iDIEL and Novus slurry families.