Low-Temperature ALD Protective Layer for FIB-SEM Metrology
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Solution Overview
Problem
Ion and electron beams used in FIB-SEM cause damage to semiconductor device structures during metrology and analysis, necessitating a protective layer that can withstand low-temperature processing without compromising substrate integrity.
Innovation Solution
A low-temperature Atomic Layer Deposition (ALD) process is employed to form a protective layer on semiconductor substrates, using precursor gases at temperatures below 100 degrees Celsius, forming an amorphous layer that reduces stress on underlying crystalline layers and protects device structures during metrology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FIB-SEM metrology and analysis are performed on semiconductor substrates, then critical dimension measurements can be obtained, but ion and electron beams cause damage to semiconductor device structures
Solution Approach 1:
A protective layer is introduced as an intermediary between the ion/electron beams and the semiconductor device structures. This protective layer absorbs the harmful beam effects while allowing the metrology measurements to proceed on the protected substrate surface.
Solution Approach 2:
The protective layer is deposited before the FIB-SEM metrology process to pre-establish protection against beam damage. This preliminary action prevents the harmful effects from reaching the underlying device structures during subsequent measurement operations.
2Strength
If high-temperature deposition processes are used to form protective layers, then dense and robust protective layers can be achieved, but thermal stress damages the underlying crystalline semiconductor layers
Solution Approach 1:
The deposition temperature parameter is changed from conventional high temperatures to low temperatures (below 100°C). This parameter change enables protective layer formation while avoiding thermal stress on the underlying crystalline semiconductor layers, as the low temperature prevents thermal expansion mismatches and stress accumulation.
Solution Approach 2:
The protective layer is formed in an amorphous phase through low-temperature deposition, which eliminates stress-related issues associated with crystalline phase transitions. The amorphous structure accommodates thermal expansion differences without generating stress on the underlying crystalline semiconductor layers.
3Stress or pressure
If low-temperature ALD process is used to deposit protective layer, then thermal stress on substrate is minimized, but deposition rate and layer quality may be compromised
Solution Approach 1:
Multiple deposition parameters are optimized for low-temperature operation: precursor chemistry is selected for reactivity at low temperatures, deposition time is extended to compensate for lower reaction rates, and pressure conditions are adjusted to enhance precursor adsorption. These parameter changes maintain layer quality and achieve sufficient deposition rates while keeping the substrate temperature below 100°C to minimize thermal stress.
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 low-temperature ALD process enables accurate and consistent CD measurements by minimizing damage from ion and electron beams, ensuring the integrity of semiconductor device structures.
Implementation Method 1
A reacting portion of the first precursor gas is absorbed onto a surface of the substrate to form a first sub-layer of the protective layer
Implementation Method 2
A reacting portion of the second precursor gas is absorbed onto the surface of the substrate to form a second sub-layer of the protective layer
Implementation Method 3
A non-reacting portion of the first precursor gas is purged from the first reaction chamber, the non-reacting portion of the first precursor gas not being absorbed onto the surface of the substrate
Data Source
AI summary
A method for depositing protective layers on a surface of a substrate includes conducting a plurality of ALD cycles in a first reaction chamber to deposit a first protective layer on the substrate. Each ALD cycle of the plurality of ALD cycles is conducted at a deposition temperature below about 100° C. and includes delivering a first precursor gas into the first reaction chamber containing the substrate. A reacting portion of the first precursor gas is absorbed onto a surface of the substrate to form a first sub-layer of the protective layer. A second precursor gas is delivered into the first reaction chamber containing the substrate, a reacting portion of the second precursor gas being absorbed onto the surface of the substrate to form a second sub-layer of the protective layer. Metrology analysis is performed on the substrate within a second reaction chamber.