Spherical Wafer Support Pins for Millisecond Anneal Stress Relief
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Solution Overview
Problem
Millisecond anneal systems face challenges in managing the rapid thermal stresses and vibrations of semiconductor wafers during ultra-fast heat treatment, which can lead to wafer fracture due to excessive stress and contact with support pins during high-speed motion.
Innovation Solution
The system employs a wafer support structure with spherical surface profile support pins and a method to determine local contact stress using surface normal estimates, allowing for reduced stress through curvature accommodation and smooth surface contact, and modifying thermal processing based on stress data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If intense and brief light exposure is used to heat the substrate surface rapidly, then the annealing effect is improved, but thermal stress and vibrations increase causing wafer fracture
Solution Approach 1:
The support pin is designed with a spherical surface profile instead of a flat or pointed contact surface. This curvature allows the support pin to accommodate varying angles of the substrate surface normal during thermal processing, distributing contact stress more evenly and preventing wafer fracture caused by intense thermal gradients and vibrations.
2Ease of manufacture
If the substrate is supported on a flat surface, then manufacturing is simple, but contact stress concentrates causing wafer fracture
Solution Approach 1:
The support pin features a spherical surface profile that replaces flat contact surfaces. This curvature distributes the contact stress over a larger area and accommodates substrate surface variations, significantly reducing concentrated stress that would otherwise cause wafer fracture during rapid thermal processing.
3Stress or pressure
If support pins with spherical surface profile are used, then contact stress is reduced, but device complexity increases
Solution Approach 1:
The support pin is designed with a spherical surface profile, which can be manufactured using standard spherical grinding or polishing techniques. While slightly more complex than flat surfaces, this geometry is well-established in precision engineering and provides significant benefits in stress distribution and substrate accommodation during thermal processing.
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 effectively reduces contact stress and prevents wafer fracture by accommodating varying surface normals and smoothing the contact interface, ensuring stable wafer support during intense thermal processing.
Implementation Method 1
At least one of the support pins has a spherical surface profile to accommodate a varying angle of a substrate surface normal at the point of contact with the substrate
Implementation Method 2
Millisecond, or ultra-fast, temperature treatment of semiconductor substrates can be achieved using an intense and brief exposure of light to heat the entire top surface of the substrate
Implementation Method 3
The rapid heating of just one surface of the substrate can produce a large temperature gradient through the thickness of the substrate, while the bulk of the substrate maintains the temperature before the light exposure
Implementation Method 4
The bulk of the substrate therefore acts as a heat sink resulting in fast cooling rates of the top surface
Data Source
AI summary
Systems and methods for substrate support in a millisecond anneal system are provided. In one example implementation, a millisecond anneal system includes a processing chamber having a wafer support plate. A plurality of support pins can extend from the wafer support plate. The support pins can be configured to support a substrate. At least one of the support pins can have a spherical surface profile to accommodate a varying angle of a substrate surface normal at the point of contact with the substrate. Other example aspects of the present disclosure are directed to methods for estimating, for instance, local contact stress at the point of contact with the support pin.