Via Contact Etch Rate Density Effect Determination

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Solution Overview

Problem

Variations in via/contact etch rates during semiconductor chip manufacturing lead to over-etch and under-etch issues due to non-uniform via/contact density patterns, causing yield loss and electrical contact failures, as the etching process is affected by reactant transport limitations and local configuration.

Innovation Solution

A method to determine the effect of via/contact pattern density on etch rates by calculating the neutral etchant species flux intersecting each via/contact mouth and comparing variations across the wafer scale, allowing for identification of under-etched or over-etched features and adjustment of layout design or etching processes to minimize failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If via/contact density patterns are non-uniform across the wafer, then local etch rate variations occur due to reactant transport limitations, but manufacturing precision deteriorates causing over-etch and under-etch

Engineering Contradiction:

Improvevia/contact etching throughputVSAvoidvia/contact etch depth uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent performs preliminary calculation of neutral etchant species flux for each via/contact location based on layout characteristics before the actual etching process. This allows identification of regions prone to under-etch or over-etch, enabling pre-compensation in process parameters or layout modification to achieve uniform etching across non-uniform density patterns

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of neutral etchant species flux distribution by considering local layout characteristics (via/contact density, spacing, patterns) to predict and compensate for etch rate variations. This involves calculating flux variations as a function of local density and adjusting process conditions accordingly

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If optical emission spectroscopy is used to detect etch stop point, then etch termination can be detected, but reliability deteriorates due to existing variation in etch rate causing some vias to be under-etched while others are over-etched

Engineering Contradiction:

Improveetch stop detection accuracyVSAvoidvia/contact etch completion consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent performs preliminary calculation of neutral etchant species flux distribution across the wafer based on layout characteristics before etching. This allows identification of regions with significantly different flux levels that will lead to under-etch or over-etch, enabling pre-compensation to ensure consistent etch completion across all via/contacts

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a feedback mechanism where the calculated neutral etchant species flux information is used to adjust etching process parameters or layout design to compensate for predicted variations, ensuring more reliable and consistent etch completion across different via/contact densities

Inventive Principle:

Principle #23Feedback

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

Enables discrimination between normal and failed vias/contacts based on etch tolerance criteria, enabling chip designers to optimize layout and manufacturers to modify processes, reducing via/contact failures and improving wafer yield.

Implementation Method 1

Using a plasma etch process to create vias in the manufacturing of semiconductor chips is known in the art

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

etchant from the plasma etches a feature

Methodology Applied

Scientific EffectIon bombardment: Ion Beam

Implementation Method 3

reactant transport (by means of gas phase diffusion and flow) limitations

Methodology Applied

Scientific EffectGas phase diffusion: Diffusion

Implementation Method 4

depletion in reactive gas species, which are needed for surface etching reactions (etchant), in the wafer regions where a higher etchant consumption occurs

Methodology Applied

Scientific EffectReactant consumption: Chemical Bonding

Data Source

PatentUS7687303B1Method for determining via/contact pattern density effect in via/contact etch rate

Publication Date: 2010.03.30 SIEMENS INDUSTRY SOFTWARE INC

AI summary

A method for determining an effect of via/contact pattern density in via/contact etch rate of a wafer includes determining a neutral etchant species number flux intersecting each via/contact mouth as a function of local layout characteristics and determining variations in the neutral etchant species flux number as a function of the via/contact pattern density in a wafer scale. The comparison of these number fluxes provides the capability to discriminate an underetched or an overetched via/contact from normal vias/contacts satisfying an etch tolerance criterion. Chip designers can modify the layout design to minimize via/contact failures. Chip manufacturers can modify the etching process to minimize via/contact failures.