Thermal Transfer Plate for Pulsed Heating
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Solution Overview
Problem
Pulsed heating in semiconductor wafer processing leads to undesirable thermal exposure and non-uniformity due to rapid temperature rise and inefficient heat transfer, causing excessive dopant diffusion and stress, which existing methods fail to adequately address.
Innovation Solution
A thermal transfer plate with a thermal mass no greater than three times that of the object is used, positioned in close thermal communication to enhance heat transfer through conduction and radiative cooling, and optionally preheated to reduce energy pulse magnitude and stress, with materials like silicon or ceramics, and gases with high thermal conductivity to facilitate efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a pulse of energy is delivered to the wafer surface over a short time scale, then the surface heating effect is enhanced, but the thermal exposure of the bulk wafer increases due to rapid heat diffusion
Solution Approach 1:
A thermal transfer plate with optimized thermal mass (no greater than three times the wafer thermal mass) is introduced as an intermediary between the wafer and the heating/cooling environment. The plate facilitates rapid heat extraction from the wafer back surface during cooling phases, limiting thermal exposure while allowing controlled surface heating during pulse delivery.
Solution Approach 2:
The thermal mass of the transfer plate is specifically controlled to be no greater than three times the thermal mass of the wafer. This parameter optimization enables the plate to efficiently absorb and remove heat from the wafer during cooling phases, thereby limiting thermal exposure time while maintaining effective surface heating capability.
2Productivity
If the thermal mass of the heatsink is increased to improve cooling efficiency, then heat transfer from the wafer is enhanced, but the ability to rapidly change wafer temperature is reduced
Solution Approach 1:
The thermal mass of the transfer plate is optimized to be no greater than three times the thermal mass of the wafer. This controlled parameter ensures the plate has sufficient capacity to extract heat during cooling phases (improving cooling efficiency) while not being so large that it prevents rapid temperature changes during heating phases.
Solution Approach 2:
The system dynamically switches between heating and cooling modes. During cooling phases, the transfer plate actively extracts heat; during heating phases, the plate's thermal mass is insufficient to prevent rapid temperature rise, thus achieving both high cooling efficiency and rapid temperature change capability.
3Use of energy by moving object
If background heating is applied to preheat the wafer, then the energy pulse magnitude can be reduced, but the thermal exposure time increases
Solution Approach 1:
Background heating is applied to preheat the wafer before the pulsed heating phase. This preliminary action reduces the magnitude of the energy pulse needed to achieve the desired surface temperature, while the optimized transfer plate compensates for the increased thermal exposure time by enabling more efficient heat management during the process.
Solution Approach 2:
The thermal mass ratio between the transfer plate and wafer is controlled (plate ≤ 3× wafer thermal mass) to optimize the balance between background heating and pulsed heating phases, allowing reduced pulse magnitude while managing overall thermal exposure through efficient heat extraction capability.
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 significantly reduces thermal exposure and non-uniformity by enhancing heat transfer from the wafer, allowing for rapid cooling and more controlled thermal processing, thereby minimizing dopant diffusion and stress, and achieving a specific thermal profile with precise temperature control.
Implementation Method 1
The thermal transfer plate enhances heat transfer from the object after the pulse has ceased by way of thermal conduction
Implementation Method 2
allows for greater heat transfer away from the object than is available by radiative cooling of the object alone
Data Source
AI summary
An approach for optimizing the thermal budget during a pulsed heating process is disclosed. A heat sink or thermal transfer plate is configured and positioned near an object, such as a semiconductor wafer, undergoing thermal treatment. The heat sink is configured to enhance the thermal transfer rate from the object so that the object is rapidly brought down from the peak temperature after an energy pulse. High thermally-conductive material may be positioned between the plate and the object. The plate may include protrusions, ribs, holes, recesses, and other discontinuities to enhance heat transfer and avoid physical damage to the object during the thermal cycle. Additionally, the optical properties of the plate may be selected to allow for temperature measurements via energy measurements from the plate, or to provide for a different thermal response to the energy pulse. The plate may also allow for pre-heating or active cooling of the wafer.