Pulsed Laser Crystallization of Semiconductor Substrates
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Solution Overview
Problem
Current methods for forming crystalline semiconductor layers are inefficient and costly, particularly as device sizes decrease, requiring high-volume, cost-effective methods to enhance electrical properties and crystal structure in semiconductor processing.
Innovation Solution
A progressive melting and recrystallization process using pulsed energy to convert amorphous or small-crystal semiconductor layers into large crystals, where pulsed laser energy is delivered to melt and resolidify specific areas of a substrate, controlling the energy and temperature to promote large crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional crystallization methods (epitaxy, annealing, deposition) are used, then crystalline semiconductor layers can be formed, but the processing time is long and production efficiency is low
Solution Approach 1:
The patent applies periodic pulsed laser irradiation to the semiconductor substrate, where the laser is delivered in repeated cycles rather than continuously. Each pulse melts a portion of the substrate, followed by a freeze period where crystallization occurs. This periodic action enables controlled progressive crystallization while maintaining high processing speeds, resolving the contradiction between manufacturing precision and productivity.
Solution Approach 2:
The patent utilizes phase transitions of the semiconductor material between solid, liquid, and crystalline states. By controlling the laser pulse parameters, the substrate undergoes rapid melting followed by controlled freezing and crystallization. This exploitation of phase transitions enables fast crystallization processes that achieve high crystal quality without the long processing times of conventional methods.
2Manufacturing precision
If slower crystallization processes are used, then atoms can find lowest energy positions and form high-quality crystals, but the processing time increases significantly
Solution Approach 1:
The patent applies preliminary action by delivering laser pulses that melt the substrate before crystallization occurs. This pre-melting action creates a liquid state that facilitates rapid atomic rearrangement and crystal nucleation when the material freezes, enabling fast formation of large-grain crystals without requiring slow thermal diffusion processes.
Solution Approach 2:
The patent changes key parameters including temperature (through controlled heating and cooling cycles), pressure (via rapid phase transitions), and time (using short laser pulse durations). These parameter changes enable the system to achieve high-quality crystal formation in reduced time by moving through phase states that favor rapid crystallization.
3Productivity
If high-volume production methods are implemented, then cost-effectiveness improves, but maintaining crystal structure quality becomes more challenging
Solution Approach 1:
The patent segments the crystallization process into discrete laser pulse cycles, where each pulse treats a specific region or layer of the substrate. This segmentation allows for precise control of crystal growth in each zone while maintaining uniformity across the entire substrate, enabling high-volume production without sacrificing crystal structure quality.
Solution Approach 2:
The patent implements feedback control by monitoring the crystallization process and adjusting laser pulse parameters (energy, duration, frequency) based on observed crystal growth characteristics. This feedback mechanism ensures consistent crystal structure quality across high-volume production runs by automatically compensating for variations in material properties or processing conditions.
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 process accelerates the formation of large crystals across semiconductor substrates, reducing processing time and thermal stresses, enabling the production of high-quality crystalline materials with improved electrical properties, suitable for advanced devices like 3D flash memory and DRAM.
Implementation Method 1
melted using a progressive melting process of delivering pulsed energy to the treatment area
Implementation Method 2
A treatment area of the substrate is identified and melted using a progressive melting process
Implementation Method 3
as the melted material freezes
Implementation Method 4
The treatment area is then recrystallized using a progressive crystallization process
Data Source
AI summary
Apparatus and methods of treating a substrate with an amorphous semiconductor layer, or a semiconductor layer having small crystals, to form large crystals in the substrate are described. A treatment area of the substrate is identified and melted using a progressive melting process of delivering pulsed energy to the treatment area. The treatment area is then recrystallized using a progressive crystallization process of delivering pulsed energy to the area. The pulsed energy delivered during the progressive crystallization process is selected to convert the small crystals into large crystals as the melted material freezes.