Atomic Layer Cleaning of Semiconductor Contacts
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Solution Overview
Problem
In integrated circuit manufacturing, the metallization process faces challenges in establishing effective electrical connections due to contaminants such as etch residues and native oxides on semiconductor substrates, which inhibit ohmic contact and require improved cleaning methods that are selective and less damaging to the substrate.
Innovation Solution
The implementation of an atomic layer clean (ALC) process using halogen-containing species to form an adsorption-limited layer on the electrical contact interface, activating a reaction to remove contaminants, and depositing a metallization layer without damaging the substrate, employing a plasma-activated surface reaction with controlled energy to ensure precise cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cleaning methods (sputter etch, wet chemical clean) are used to remove contaminants from the contact interface, then cleaning effectiveness is improved, but substrate damage increases and critical dimensions are compromised
Solution Approach 1:
The invention changes the chemical parameters of the cleaning process by using fluorine-based chemistry (SF6, CF4 gases) instead of traditional physical sputtering or wet chemicals. This chemical approach selectively removes contaminants through fluorocarbon formation and desorption at controlled temperatures (200-400°C), achieving effective cleaning while minimizing substrate damage and preserving critical dimensions
Solution Approach 2:
The invention replaces mechanical/physical cleaning methods (sputter etching with ion bombardment) with a chemical vapor deposition-based cleaning process. The fluorine-containing gases chemically react with contaminants to form volatile fluorocarbon species that are subsequently removed, eliminating the need for high-energy ion bombardment that causes substrate damage
2Reliability
If aggressive cleaning processes are applied to ensure complete contaminant removal, then cleaning completeness is improved, but contact dimension control deteriorates
Solution Approach 1:
The cleaning process is divided into periodic sequential steps: (1) fluorine exposure to form fluorocarbon on contaminants, (2) purging to remove excess gas, (3) thermal or plasma activation to desorb fluorocarbon, and (4) another purge. This periodic cyclic approach ensures complete contaminant removal while precisely controlling the duration and intensity of each step to preserve contact dimensions
Solution Approach 2:
The process uses controlled parameter changes including temperature (200-400°C), pressure (1-100 mTorr), and gas flow rates to optimize the cleaning reaction. By carefully adjusting these parameters, the process achieves complete contaminant removal while limiting material removal from the contact itself, thus maintaining manufacturing precision
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 ALC process effectively removes contaminants with high precision, minimizing substrate damage and maintaining the critical dimensions and aspect ratios of the contact region, enabling reliable ohmic contact and improved metallization quality.
Implementation Method 1
forming an adsorption-limited layer, which includes halogen from the halogen-containing species, atop the electrical contact interface
Implementation Method 2
exposing the adsorption-limited layer to an ion and/or free-radical species of a plasma
Data Source
AI summary
Described are cleaning methods for removing contaminants from an electrical contact interface of a partially fabricated semiconductor substrate. The methods may include introducing a halogen-containing species into a processing chamber, and forming an adsorption-limited layer, which includes halogen from the halogen-containing species, atop the electrical contact interface and/or the contaminants thereon. The methods may further include thereafter removing un-adsorbed halogen-containing species from the processing chamber and activating a reaction between the halogen of the adsorption-limited layer and the contaminants present on the electrical contact interface. The reaction may then result in the removal of at least a portion of the contaminants from the electrical contact interface. In some embodiments, the halogen adsorbed onto the surface and reacted may be fluorine. Also described herein are apparatuses having controllers for implementing such electrical contact interface cleaning techniques.