Back-Surface Spike Annealing for Semiconductor Uniformity
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Solution Overview
Problem
Conventional thermal processing methods face challenges in achieving high spatial resolution and uniformity during spike annealing, particularly in delivering short peak width spike anneals at low temperatures without pattern effects and non-uniformity, and in controlling thermal budgets to prevent dopant diffusion and excessive oxidation.
Innovation Solution
A method involving a thermal processing system where a workpiece is heated by delivering an energy pulse to its non-device side surface with a pulse duration less than the thermal conduction time through its thickness, resulting in a rapid heating rate greater than 1000 K/s and a controlled cooling rate, allowing for asymmetrical spike heating profiles and reduced thermal budgets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal processing methods are used for spike annealing, then heating can be applied to the device side surface, but spatial resolution and uniformity deteriorate due to pattern effects and non-uniformity
Solution Approach 1:
The patent applies inversion by heating the non-device side surface (back surface) instead of the device side surface (front surface). This reverses the conventional approach and eliminates pattern effects because the heating source does not directly illuminate the device structures, thereby achieving uniform heating with high spatial resolution across the entire wafer surface.
Solution Approach 2:
The patent uses the wafer substrate itself as an intermediary to transfer heat from the non-device side surface to the device side surface. By heating through the back surface, the wafer acts as a heat conductor that distributes thermal energy uniformly to the front surface where device structures reside, avoiding direct exposure to the heat source and eliminating associated pattern effects.
2Reliability
If longer pulse duration is used for heating, then more complete annealing can be achieved, but dopant diffusion increases due to extended thermal exposure
Solution Approach 1:
The patent employs periodic pulsed heating with carefully controlled pulse durations (e.g., 1-100 milliseconds). These repeated short pulses deliver the necessary thermal energy for complete annealing while limiting the total time at elevated temperatures, thereby preventing excessive dopant diffusion. The periodic nature allows thermal energy to accumulate effectively while maintaining tight control over thermal budget.
Solution Approach 2:
The patent changes the temporal parameters of heating by using pulsed sequences with specific pulse widths and duty cycles. By adjusting pulse duration, frequency, and total heating time, the process achieves complete annealing效果 while minimizing dopant diffusion. This parameter optimization allows decoupling of annealing completeness from thermal exposure time.
3Loss of substance
If higher heating rates are applied, then thermal budget is reduced and dopant diffusion is minimized, but thermal stress increases
Solution Approach 1:
The patent applies local quality by creating controlled thermal gradients through the wafer thickness. The back surface experiences higher temperatures while the front surface with device structures maintains more moderate temperatures. This spatial differentiation of thermal conditions allows high heating rates at the heating interface while protecting device regions from excessive thermal stress through the thermal mass and conductivity of the substrate.
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 spike anneal uniformity with high spatial resolution, reduces dopant diffusion, and minimizes thermal stress, enabling effective annealing at high temperatures while maintaining low thermal budgets, thus preventing degradation of semiconductor devices.
Implementation Method 1
The pulse duration is less than a thermal conduction time for heat from the energy pulse to diffuse through the thickness of the workpiece
Data Source
AI summary
Methods and systems for providing a short-duration anneal are provided. In one example, the methods and systems can include placing a workpiece in a thermal processing chamber. The workpiece can include a device side surface and an opposing non-device side surface. The methods and systems can include delivering an energy pulse from at least one heat source to the non-device side surface of the workpiece. In another example, the methods and systems can include depositing a layer of semiconductor material onto the semiconductor workpiece at the device side of the semiconductor workpiece. The methods and systems can include doping the layer of semiconductor material with a doping species and annealing the layer for crystallization using solid phase epitaxy.