Cobalt Silicide CoSi2 Formation by Solid-State Laser Annealing

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Solution Overview

Problem

Existing methods for manufacturing cobalt silicide CoSi2 face challenges such as nucleation difficulties during the CoSi/CoSi2 transition, especially at small dimensions, leading to non-planar interfaces and integration issues, and require multiple high-temperature annealing steps that are costly and complex.

Innovation Solution

A single-step pulsed laser annealing process is used to form CoSi2 in the solid state, avoiding the CoSi/CoSi2 transition, ensuring a planar interface and compatibility with three-dimensional integration, using laser pulses with controlled energy density and frequency to maintain the material in a solid phase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If two-step RTA process is used to form CoSi2, then CoSi2 can be formed through CoSi intermediate layer, but the interface becomes non-planar and nucleation difficulties occur

Engineering Contradiction:

Improveinterface planarityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the problematic CoSi intermediate phase from the formation process. By using a single-step laser annealing process that directly transforms Co and Si into CoSi2 without forming CoSi, the method removes the source of interface non-planarity and nucleation difficulties that plague the traditional two-step RTA process.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention employs periodic pulsed laser annealing instead of continuous heating. The pulsed nature of the laser delivers energy in controlled intervals, enabling direct transformation to CoSi2 while maintaining thermal control and avoiding the intermediate CoSi phase formation, thus achieving planar interfaces.

Inventive Principle:

Principle #19Periodic action

2Productivity

If nanosecond laser annealing is used to form CoSi2 in liquid state, then CoSi2 can be formed quickly, but significant stresses occur and additional annealing is needed

Engineering Contradiction:

Improveformation speedVSAvoidwafer stress

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the key parameter of laser pulse duration from nanosecond scale to microsecond scale (at least 1 microsecond). This parameter change fundamentally alters the heating mechanism, allowing sufficient time for solid-state diffusion and direct CoSi2 formation without liquid phase transition, thereby eliminating wafer stress while maintaining formation speed.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention deliberately avoids the liquid phase transition of CoSi2 that occurs with nanosecond laser annealing. By using microsecond pulses, the process remains in the solid state throughout, preventing the formation of liquid CoSi2 that causes significant thermal stress and requires additional annealing steps for defect removal.

Inventive Principle:

Principle #36Phase transitions

3Length of moving object

If smaller contact dimensions are used (CD < 100 nm), then device scaling is achieved, but surface energy becomes too low and CoSi zones remain

Engineering Contradiction:

Improvecontact dimensionVSAvoidsilicide formation completeness

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The invention performs preliminary action by ensuring complete CoSi2 formation through controlled microsecond laser annealing before any subsequent processing. The extended pulse duration ensures that even at small dimensions where surface energy effects dominate, the transformation from Co to CoSi2 is complete, preventing residual CoSi zones that would compromise device performance.

Inventive Principle:

Principle #10Preliminary 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

The method achieves a planar CoSi2/Si interface, reduces integration problems, and maintains comparable sheet resistance and critical superconductivity temperature, while eliminating the need for multiple annealing steps and reducing material stress.

Implementation Method 1

annealing the stack by a nanosecond laser comprising at least one laser pulse with a duration between 50 nanoseconds and 20 microseconds

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

an energy density selected so as to form the cobalt silicide CoSi2 layer in the solid state

Methodology Applied

Scientific EffectThermal energy transfer: Conduction (thermal)

Data Source

PatentUS20250313481A1PROCESS FOR MANUFACTURING COBALT SILICIDE CoSi2

Publication Date: 2025.10.09 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

The invention relates to a method for manufacturing a cobalt silicide CoSi2 layer including the steps of:Providing a substrate comprising a silicon layer;Depositing a cobalt Co layer onto the substrate;Annealing the stack by a nanosecond laser comprising at least one laser pulse with a duration between 50 nanoseconds and 20 microseconds and an energy density selected so as to form the cobalt silicide CoSi2 layer in the solid state.