Contact Hole Etch Feedback Control for Polymer Bridging

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Solution Overview

Problem

In sub-45 nm semiconductor devices, the narrow process window for metal contact etch patterning leads to a high risk of open-failures due to polymer bridging, which restricts the flow of etchant and results in inadequate etching, making it challenging to achieve a small final critical dimension without incurring open or short circuit failures.

Innovation Solution

Implementing a transition etch step with closed-loop feedback to control the percentage of oxygen in the etching chamber, which enlarges the temporary inner diameter near the top of the contact hole, optimizing the flow of etchant to the bottom and managing polymer restrictions, thereby preventing open failures and achieving a desired final critical dimension.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If polymerizing gas chemistry is applied to shrink the critical dimension, then the final critical dimension is reduced, but the risk of open-failures increases

Engineering Contradiction:

Improvefinal critical dimensionVSAvoidopen-failure risk

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The etch process is divided into multiple distinct steps: a first oxide etch step, a transition etch step with oxygen feedback control, and a second oxide etch step. This segmentation allows each step to perform a specific function - the transition step specifically addresses polymer management while the other steps focus on dimension control, thereby reducing open-failures while achieving small critical dimensions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A closed-loop feedback system measures the oxygen percentage in the etching chamber in real-time and dynamically adjusts the oxygen flow rate during the transition etch step. This feedback control ensures optimal etchant flow through the contact hole by maintaining the correct oxygen level, preventing both open-failures and short-circuits while achieving the target critical dimension

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If a small final critical dimension is achieved, then overlay margin is extended, but the process window becomes narrower

Engineering Contradiction:

Improvefinal critical dimensionVSAvoidprocess window

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The transition etch step dynamically adjusts oxygen flow rates based on real-time oxygen percentage measurements to compensate for variations in contact hole dimensions. This dynamic adaptation allows the process to maintain small critical dimensions while being tolerant to process variations, effectively widening the process window

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The process changes multiple parameters including oxygen percentage, oxygen flow rate, and etch duration in the transition step. These parameter changes are coordinated to achieve small critical dimensions while maintaining process robustness against variations in other process conditions

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the top of the contact hole is enlarged to increase etchant flow, then open-failures are prevented, but the top critical dimension increases

Engineering Contradiction:

Improveopen-failure preventionVSAvoidtop critical dimension

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The transition etch step performs preliminary action by enlarging the top of the contact hole before the final etch step. This preliminary enlargement ensures adequate etchant flow reaches the bottom of the contact hole during subsequent steps, preventing open-failures while the final step maintains the tight top critical dimension specification

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The etch process is segmented so that the transition step specifically addresses etchant flow management by enlarging the contact hole top, while the final etch step focuses on achieving the precise top critical dimension. This functional segmentation resolves the contradiction between preventing open-failures and maintaining small top dimensions

Inventive Principle:

Principle #1Segmentation

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 significantly reduces open circuit failures while maintaining a small critical dimension, allowing for a larger bottom critical dimension to prevent open failures and a smaller top dimension to prevent short circuit failures, thereby enhancing the yield and precision of the etching process.

Implementation Method 1

metal contact etch patterning

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

controlling the percentage of oxygen in the etching chamber to enlarge a temporary inner diameter

Methodology Applied

Scientific EffectGas flow control:

Implementation Method 3

polymerizing gas chemistry has been applied to the etch process

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentUS8236699B2Contact patterning method with transition etch feedback

Publication Date: 2012.08.07 SAMSUNG ELECTRONICS CO LTD

AI summary

A method for forming a contact hole in a semiconductor device and related computer-readable storage medium are provided, the method and program steps of the medium including measuring a percentage of oxygen in an etching chamber, and controlling the percentage of oxygen in the etching chamber to enlarge a temporary inner diameter near a top of the contact hole.