Tungsten Film Etch Selectivity via Fluorine Species

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Solution Overview

Problem

The deposition of tungsten-containing films into high aspect ratio features often results in seam formation, leading to increased resistance and material loss, as the deposited layer seals off void spaces, preventing further precursor entry and causing keyholes that are difficult to fill without unwanted side effects during etch and deposition cycles.

Innovation Solution

A method involving chemical vapor deposition (CVD) and atomic layer deposition (ALD) with activated fluorine species to selectively etch tungsten-containing films more than underlying materials, controlling temperature to achieve high etch selectivity and repeat etching and deposition steps to fill recessed features without removing tungsten from the bottom, while using CMP to address seam issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If tungsten-containing film is deposited into high aspect ratio features using CVD, then the features are filled with conductive material, but seams form inside the features causing high resistance and contamination

Engineering Contradiction:

Improvefilling qualityVSAvoidseam formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic deposition-etch cycles where tungsten film is deposited partially, then etched back selectively, repeated multiple times to progressively fill the feature without forming seams. This periodic action allows controlled material addition and removal to eliminate void spaces

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes process parameters including temperature (heating substrate to 30-150°C), etchant concentration, and deposition conditions to optimize selective etching of tungsten while preserving liner/barrier layer, enabling precise control over film thickness and seam prevention

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If etch back step is performed with fluorine species to remove tungsten from field and overhang, then unwanted side effects occur including removal of tungsten inside the via

Engineering Contradiction:

Improveoverhang removalVSAvoidtungsten removal from via

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent applies local quality by creating different surface conditions - the liner/barrier layer overhang is exposed and more susceptible to etching, while the bottom of the via retains tungsten protected by the liner. The etchant selectively attacks exposed tungsten surfaces while preserving protected regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The liner/barrier layer acts as an intermediary that protects the tungsten at the bottom of the via during etch back steps. This intermediate layer enables selective removal of overhang tungsten while preserving the via fill tungsten through differential etching rates

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If deposition-etch cycles are repeated to reduce keyhole, then the keyhole void remains difficult to fill without unwanted side effects

Engineering Contradiction:

Improvekeyhole reductionVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent uses partial filling followed by selective etching rather than attempting complete fill in one step. The excessive deposition beyond the keyhole is intentionally created and then selectively removed, allowing precise control over the final fill shape without compromising the keyhole region

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables seam-free filling of features with enhanced etch selectivity, reducing keyhole formation and improving the integration of tungsten films by allowing precise control over etch thickness and minimizing material loss, thus enhancing the performance of integrated circuits.

Implementation Method 1

using an etchant including activated fluorine species to selectively etch the tungsten-containing film more than an underlying material of the recessed feature

Methodology Applied

Scientific EffectSelective etching:

Implementation Method 2

filling a recessed feature of a substrate with tungsten-containing film using at least one of chemical vapor deposition (CVD) and atomic layer deposition (ALD)

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 3

using an etchant including activated fluorine species to selectively etch the tungsten-containing film

Methodology Applied

Scientific EffectChemical reaction:

Data Source

PatentUS8883637B2Systems and methods for controlling etch selectivity of various materials

Publication Date: 2014.11.11 NOVELLUS SYSTEMS INC

AI summary

A method for filling a recessed feature of a substrate includes a) at least partially filling a recessed feature of a substrate with tungsten-containing film using at least one of chemical vapor deposition (CVD) and atomic layer deposition (ALD); b) at a predetermined temperature, using an etchant including activated fluorine species to selectively etch the tungsten-containing film more than an underlying material of the recessed feature without removing all of the tungsten-containing film at a bottom of the recessed feature; and c) filling the recessed feature using at least one of CVD and ALD.