TiN Hard Mask Via Control Mitigating Oxide Etch Blowout

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Solution Overview

Problem

The existing semiconductor wafer fabrication processes face challenges in controlling via critical dimension due to 'blowout' phenomena during the etching of oxide layers, leading to irregular via diameters and spacing issues.

Innovation Solution

The implementation of a titanium nitride (TiN) hard mask layer, where an Nblock layer is deposited onto a semiconductor substrate, followed by a TiN layer and an oxide layer, allowing for partial-depth via hole formation aligned with metal deposits, and subsequent etching through the oxide layer using selective dry chemistries to mitigate blowout and maintain consistent via diameter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If oxide layer is etched to form via holes, then via holes are formed to contact metal deposits, but blowout occurs during etching leading to irregular via diameters

Engineering Contradiction:

Improvevia diameter controlVSAvoidblowout during etching

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

A titanium nitride (TiN) hard mask layer is introduced as an intermediary layer between the oxide layer and the Nblock layer. This TiN layer serves as a protective barrier during the oxide etching process, preventing the etchant from attacking the Nblock layer and causing blowout. The TiN layer is selectively removed after via formation using TiN-selective chemistry, allowing clean via holes with controlled dimensions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The TiN hard mask layer is deposited in advance before the oxide layer formation. This preliminary action creates a protective barrier that prevents blowout during subsequent oxide etching. The TiN layer is positioned strategically to protect the Nblock layer from etchant attack while allowing the oxide layer to be etched cleanly to form via holes.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If via holes are formed through oxide layer, then contact to metal deposits is achieved, but spacing between vias and metal lines is reduced leading to manufacturing difficulties

Engineering Contradiction:

Improvevia to metal contactVSAvoidspacing control

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The TiN hard mask layer acts as a spacer that maintains proper distance between via holes and adjacent metal lines. By preventing blowout during oxide etching, the TiN layer ensures that via holes are formed with precise dimensions and appropriate spacing, making subsequent manufacturing steps easier and more reliable.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 results in well-defined via diameters with minimal blowout and vertical via formation, improving the minimum spacing between vias and adjacent metal lines, thereby enhancing the precision and reliability of semiconductor wafer interconnects.

Implementation Method 1

depositing a titanium nitride (TiN) layer directly onto the Nblock layer

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

subsequent etching through the oxide layer using selective dry chemistries to mitigate blowout and maintain consistent via diameter

Methodology Applied

Scientific EffectSelective dry etching:

Data Source

PatentUS10886197B2Controlling via critical dimension with a titanium nitride hard mask

Publication Date: 2021.01.05 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An Nblock layer is deposited onto a semiconductor substrate that includes metal deposits. A titanium nitride (TiN) layer is deposited directly onto the Nblock layer; an oxide layer is deposited directly onto the TiN layer; and a via hole is formed through the oxide and TiN layer to contact bottom interconnect. The via hole is aligned to one of the metal deposits in the substrate.