Laser Rapid Thermal Process for Semiconductor Substrate Heating
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Solution Overview
Problem
Conventional rapid thermal processes face challenges with temperature non-uniformity and substrate breakage due to thermal stress, particularly in semiconductor fabrication, where long pre-heating and cooling times using chucks are costly and inefficient, and existing solutions struggle to improve heating performance without significant hardware modifications.
Innovation Solution
A rapid thermal process method utilizing a first laser beam for local pre-heating and a second laser beam for rapid heating, with an automatic power control system to real-time regulate process parameters, allowing for localized heating of semiconductor substrates without the need for chuck modifications, thereby reducing thermal stress and process time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chuck with heater is used to pre-heat the whole substrate to critical temperature, then free carriers are generated for laser annealing, but temperature non-uniformity occurs and substrate breakage happens due to thermal stress
Solution Approach 1:
The patent replaces the mechanical chuck heating system with a laser-based pre-heating system. Instead of using a chuck with heater that contacts the substrate, the invention uses a laser beam to scan and heat the substrate from above, eliminating the mechanical contact and associated thermal stress problems while achieving uniform temperature distribution
Solution Approach 2:
The patent applies preliminary pre-heating action before the main laser annealing process. By scanning the substrate with a laser beam at lower power density first, the substrate is gradually heated to an optimal temperature range, creating uniform thermal conditions that prevent breakage during the subsequent high-power laser annealing
2Temperature
If vacuum or electrostatic chucks are used to improve wafer temperature uniformity, then temperature distribution improves, but wafer breakage still occurs due to unbalanced adsorptive power and thermal stress
Solution Approach 1:
The patent eliminates the vacuum or electrostatic chuck system entirely and replaces it with a contactless laser scanning heating system. This substitution removes the source of unbalanced adsorptive power and associated thermal stresses that cause wafer breakage, while still achieving uniform temperature distribution through the scanning laser beam
3Manufacturing precision
If the laser scan process takes 3 to 10 minutes, then the substrate is heated to high temperature for completing annealing, but the long process time increases thermal budget and reduces productivity
Solution Approach 1:
The patent uses a two-stage laser approach where preliminary low-power scanning heats the substrate uniformly first, preparing it for the main annealing process. This preliminary action reduces the total time required for high-temperature annealing by starting the substrate in an optimal thermal state, thereby improving throughput while maintaining annealing quality
Solution Approach 2:
The patent employs periodic scanning motion of the laser beam across the substrate in multiple passes. This periodic action allows efficient heat distribution throughout the substrate area, reducing the overall process time compared to stationary heating methods while ensuring uniform annealing quality
4Productivity
If the laser beam rapidly heats the substrate to 1200° C. or higher, then annealing or re-crystallization is completed quickly, but substrate breakage occurs due to thermal stress from rapid temperature change
Solution Approach 1:
The patent applies preliminary low-power laser scanning to gradually heat the substrate to an intermediate temperature before applying high-power rapid heating. This preliminary thermal preparation reduces the temperature differential shock, allowing rapid heating to 1200°C or higher without causing substrate breakage from thermal stress
Solution Approach 2:
The patent uses the preliminary laser scanning phase as a cushioning step that prepares the substrate thermally for the subsequent rapid high-temperature annealing. This beforehand cushioning prevents thermal shock and substrate breakage by ensuring the substrate is already at an optimal temperature state before rapid heating begins
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 effectively lowers the thermal budget, reduces substrate breakage risk, and improves temperature uniformity, enabling faster and more efficient semiconductor processing while maintaining control over heating parameters in real-time without modifying existing tool hardware.
Implementation Method 1
performing a locally pre-heating process by means of a first laser beam to at least a first portion of the substrate
Implementation Method 2
performing a rapid heating process to the pre-heated first portion of the substrate
Data Source
AI summary
A rapid thermal process method contains providing a substrate, performing a pre-heating process to at least a first portion of the substrate by means of a first laser beam, and performing a rapid heating process to the pre-heated first portion of the substrate by means of a second laser beam.