Laser Surface Treatment for Strained Silicon MOS Devices
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Solution Overview
Problem
Conventional techniques face challenges in forming high-quality epitaxial silicon germanium materials for strained MOS devices as device sizes decrease, limiting circuit density and performance improvements.
Innovation Solution
A method involving a semiconductor substrate with contaminants, including a carbon species, undergoes a wet processing step to remove the oxide layer, followed by a rapid laser treatment process to increase the surface temperature above 1000°C for less than 1 second, and then quickly reduces the temperature to 300-600°C, facilitating epitaxial material growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth techniques are used for silicon germanium materials, then the process is compatible with existing fabrication facilities, but the quality of epitaxial materials deteriorates as device sizes decrease to 90 nanometers and less
Solution Approach 1:
The patent applies rapid thermal processing by changing the temperature parameter dynamically - heating the substrate to high temperatures (above 700°C) for very short durations (less than 1 second) to remove carbon contaminants, then quickly cooling. This parameter change enables high-quality epitaxial growth at smaller device sizes by eliminating contamination without requiring prolonged high-temperature exposure that would damage sub-90nm structures.
Solution Approach 2:
The invention uses periodic rapid thermal cycles consisting of brief heating pulses followed by rapid cooling. This periodic action allows repeated contamination removal and surface preparation steps, enabling high-quality epitaxial growth on sub-90nm devices by cycling through temperature states to maintain surface purity without sustained thermal exposure.
2Object-affected harmful factors
If longer high-temperature processing is used to remove contaminants, then contaminant removal is more complete, but thermal damage to sub-90nm device structures increases
Solution Approach 1:
The patent rushes through the high-temperature phase by limiting exposure to less than 1 second, quickly heating to remove carbon contaminants then immediately cooling. This skipping approach removes contaminants effectively while avoiding prolonged thermal exposure that would cause damage to sensitive sub-90nm device structures.
Solution Approach 2:
The invention dynamically changes the temperature parameter from room temperature to above 700°C and back within less than 1 second. This rapid parameter change enables complete contaminant removal during the brief high-temperature window while preventing thermal damage through immediate cooling, solving the contradiction between removal effectiveness and thermal damage.
3Productivity
If device feature sizes are reduced to increase circuit density, then more devices can be fabricated per wafer, but conventional epitaxial processes can no longer maintain material quality
Solution Approach 1:
The patent uses rapid thermal processing with temperatures above 700°C for less than 1 second to prepare surfaces for epitaxial growth on sub-90nm devices. This parameter change enables high-quality material formation at smaller scales by removing carbon contaminants that accumulate during fabrication, allowing circuit density increases without sacrificing epitaxial material quality.
Solution Approach 2:
The invention performs preliminary rapid thermal processing to remove carbon contaminants before epitaxial growth on sub-90nm devices. This preliminary action prepares the surface in advance, ensuring high-quality epitaxial material formation is possible at smaller device sizes, thereby enabling increased circuit density without quality degradation.
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 enhances device yields, reduces thermal budget, and is compatible with conventional processes, allowing for higher device packing density and performance without significant equipment modifications.
Implementation Method 1
subjecting the surface region to a laser treatment process for a time period of less than 1 second to increase a temperature of the surface region to greater than 1000 degrees Celsius
Implementation Method 2
subjecting the surface region to a rapid thermal process to remove carbon species and other contaminants from the silicon surface
Implementation Method 3
The rapid thermal process includes quickly cooling a temperature of the surface region to about 300 to about 600 degrees Celsius in less than 1 second
Data Source
AI summary
A method for fabricating semiconductor devices, e.g., strained silicon MOS device, includes providing a semiconductor substrate (e.g., silicon wafer) having a surface region, which has one or more contaminants and an overlying oxide layer. The one or more contaminants is at least a carbon species. The method also includes processing the surface region using at least a wet process to selectively remove the oxide layer and expose the surface region. The method further includes subjecting the surface region to a laser treatment process for a time period of less than 1 second to increase a temperature of the surface region to greater than 1000 degrees Celsius to remove the one or more contaminants provided on the surface region. The method also includes removing the laser treatment process to cause a reduction in temperature to about 300 to about 600 degrees Celsius in a time period of less than 1 second.