Light Diffusion Plate Venting for Uniform Flash Heat Treatment
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Solution Overview
Problem
In heat treatment apparatuses using flash lamps, the nonuniformity of illuminance distribution leads to variations in temperature distribution across the substrate, and the use of a light diffusion plate can result in slipping due to trapped air between the plate and the quartz window.
Innovation Solution
The heat treatment apparatus incorporates an air escape mechanism, such as through holes or grooves, in the light diffusion plate or the quartz window, which allows air to escape and prevents the sliding of the light diffusion plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light diffusion plate is placed on the quartz window to improve illuminance uniformity, then the in-plane uniformity of illuminance distribution is improved, but air becomes trapped between the contact surfaces causing the light diffusion plate to slip and move
Solution Approach 1:
The contact surface between the light diffusion plate and quartz window is segmented into multiple discrete contact points rather than a continuous contact surface. This is achieved by forming protrusions on one component and corresponding recesses on the other, creating localized contact regions that allow air to escape while maintaining sufficient contact area for optical function and mechanical stability.
Solution Approach 2:
The air escape paths are designed and formed in advance during manufacturing, before the components are assembled and before air trapping can occur. The protrusions and recesses are pre-formed features that automatically provide air escape channels when the components are brought into contact, preventing the air trapping problem before it arises.
2Area of stationary object
If the flash lamps are disposed in a region considerably larger than the area of the semiconductor wafer, then the coverage area is improved, but the illuminance of the peripheral portion becomes lower than the central portion causing nonuniform illuminance distribution
Solution Approach 1:
The light diffusion plate is designed with spatially varying properties to compensate for the nonuniform illuminance distribution. The protrusions are strategically positioned and sized to redirect light preferentially toward peripheral regions that receive less illumination, while central regions maintain their higher illuminance levels. This creates a more uniform overall distribution across the entire wafer surface.
Solution Approach 2:
The light diffusion plate acts as an intermediary optical element between the flash lamps and the semiconductor wafer. It receives nonuniform light from the lamps and redistributes it uniformly across the wafer surface through the protrusion-recess mechanism, decoupling the lamp arrangement from the final illuminance distribution pattern.
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
The air escape mechanism ensures a uniform illuminance distribution and prevents the light diffusion plate from slipping, thereby maintaining consistent temperature distribution across the substrate during heat treatment.
Implementation Method 1
a light diffusion plate placed on an upper surface of the chamber window and for diffusing the light emitted from the flash lamp
Implementation Method 2
the transparent quartz of the chamber window and the transparent quartz of the light diffusion plate come in contact with each other. At this time, minute flaws in the surfaces cause a mass of air to enter between the contact surfaces in some cases. As the semiconductor wafer is heat-treated, the air mass is also heated to a higher temperature to thermally expand.
Data Source
AI summary
A light diffusion plate is placed on an upper surface of an upper chamber window. A blasting process is applied to a lower surface of the light diffusion plate to provide the lower surface in the form of frosted glass. When the light diffusion plate is placed on the upper surface of the upper chamber window, the light diffusion plate and the upper chamber window do not closely adhere to each other. The frosted glass releases a mass of air entering between contact surfaces of the light diffusion plate and the upper chamber window to the outside even if the mass of air thermally expands during heat treatment. This restrains the occurrence of a phenomenon in which a thin layer of air is trapped between the light diffusion plate and the upper chamber window to prevent the sliding of the light diffusion plate resulting from the air layer.