Microwave-Laser Annealing for Fast Wafer Heating and Defect Control
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Solution Overview
Problem
Current annealing processes for semiconductor substrates, such as Rapid Thermal Processing and impulse annealing, ramp temperature too slowly and expose wafers to elevated temperatures for too long, especially with increasing wafer sizes, switching speeds, and decreasing feature sizes, leading to suboptimal performance due to defects in semiconductor materials.
Innovation Solution
A system combining continuous microwave energy with pulsed laser energy, where the pulsed laser source delivers nanosecond pulses perpendicular to the substrate, synchronized with the microwave energy to control temperature and defect generation/annihilation, achieving a unique material state and improved crystalline structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional thermal annealing processes (RTP or impulse annealing) are used, then the substrate can be heated to high temperatures for crystalline structure recovery, but the temperature ramps too slowly and the wafer is exposed to elevated temperatures for too long
Solution Approach 1:
The patent combines two different heating mechanisms - microwave heating and laser heating - into a single annealing process. The microwave source provides bulk heating while the laser source provides localized, rapid heating, together achieving faster temperature ramps than either method alone could provide.
Solution Approach 2:
The laser source operates in pulsed mode rather than continuous, delivering energy in periodic bursts. This allows for rapid temperature increases during pulse periods while avoiding excessive total exposure time, resolving the contradiction between achieving high temperature and minimizing exposure duration.
2Reliability
If conventional thermal annealing processes are used, then dopant activation can occur, but defects in semiconductor materials degrade device performance
Solution Approach 1:
The laser source provides localized heating to specific regions of the substrate where dopant activation is needed, rather than heating the entire wafer uniformly. This localized approach activates dopants in target areas while minimizing thermal exposure and defect generation in other regions, thereby improving device performance.
Solution Approach 2:
The patent changes the heating parameters by using ultrafast laser pulses with specific pulse durations and repetition rates. These parameter changes enable rapid heating cycles that activate dopants without allowing sufficient time for defect formation and diffusion, thus improving material quality and device performance.
3Productivity
If the annealing process is optimized for speed, then productivity improves, but manufacturing precision may be compromised
Solution Approach 1:
The system incorporates feedback control where the microwave and laser sources are coordinated based on process monitoring. This feedback mechanism ensures that even with faster processing speeds, the crystalline structure recovery and dopant activation are completed with the necessary precision, maintaining manufacturing quality while improving throughput.
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 the annealing process by efficiently managing temperature and defects, leading to improved semiconductor device performance and reduced resistivity in doped regions, suitable for advanced semiconductor devices like CMOS FETs and photovoltaic devices.
Implementation Method 1
a pulsed source of electromagnetic energy positioned to deliver pulses of electromagnetic energy to the substrate
Implementation Method 2
a continuous source of microwave energy positioned to deliver microwave energy to the substrate
Data Source
AI summary
A method and system for including a microwave anneal combined with a nanosecond laser pulse are provided. The method may include applying continuous electromagnetic energy from a first electromagnetic energy source to a substrate, wherein the substrate has a major surface. The method may further include exposing the substrate to laser pulses from a second electromagnetic energy source while applying the continuous electromagnetic energy, wherein exposing the substrate to each pulse of the laser pulses occurs in phase with the continuous electromagnetic energy.