Serial Irradiation of Substrate by Multiple Radiation Sources
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Solution Overview
Problem
Rapid thermal annealing of silicon wafers using electromagnetic radiation results in non-uniform heating due to constructive and destructive interference at dielectric layer interfaces, leading to incomplete thermal equilibrium over small length scales relevant to VLSI die sizes.
Innovation Solution
Configuring multiple radiation sources with different wavelengths and angular distributions to serially irradiate a substrate in independent exposure steps, where each step uses only one source to maximize energy flux and minimize error in energy transmission across multiple stacks, ensuring uniform energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electromagnetic radiation is used for rapid thermal annealing of silicon wafers, then heating speed is improved, but spatial uniformity of thermal annealing deteriorates due to constructive and destructive interference at dielectric layer interfaces
Solution Approach 1:
The invention divides the substrate into multiple regions with different dielectric stack configurations. By segmenting the substrate into regions that experience different interference patterns, the system can deliver non-uniform energy flux that compensates for the interference effects, achieving uniform thermal annealing across the entire substrate surface.
Solution Approach 2:
The invention applies local quality by tailoring the energy flux distribution to match the specific requirements of different substrate regions. Each region receives a customized energy flux based on its dielectric stack configuration, allowing the system to overcome local interference effects and achieve uniform thermal processing across the substrate.
2Manufacturing precision
If multiple radiation sources are used to improve spatial uniformity, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The invention employs dynamic control of radiation sources, where the intensity and wavelength of each source are adjusted in real-time based on the specific requirements of different substrate regions. This dynamic adjustment allows a smaller number of sources to achieve the same uniformity effect that would require many fixed sources.
Solution Approach 2:
The invention changes parameters such as wavelength, intensity, and angular distribution of the radiation sources to optimize the energy flux distribution. By varying these parameters, the system can achieve uniform thermal annealing with fewer sources compared to using a fixed configuration of multiple sources.
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 improves the spatial uniformity of thermal annealing, achieving thermal equilibrium over smaller length scales by optimizing energy flux distribution across the substrate.
Implementation Method 1
Rapid thermal anneal of a silicon wafer is often effected through direct exposure of the wafer to electromagnetic radiation
Implementation Method 2
electromagnetic radiation on time scales below 0.1 s
Implementation Method 3
constructive and destructive interference occur due to reflections at each interface in the path of the incident radiation
Implementation Method 4
constructive and destructive interference occur due to reflections at each interface
Implementation Method 5
The length (L) over which thermal equilibrium is achieved can be approximated by L ̃(t*k/cv)1/2, where k and cv are the thermal conductivity and specific heat of silicon
Data Source
AI summary
A system for configuring and utilizing J electromagnetic radiation sources (J≧2) to serially irradiate a substrate. Each source has a different function of wavelength and angular distribution of emitted radiation. The substrate includes a base layer and I stacks (I≧2; J≦I) thereon. Pj denotes a normally incident energy flux on each stack from source j. In each of I independent exposure steps, the I stacks are concurrently exposed to radiation from the J sources. Vi and Si respectively denote an actual and target energy flux transmitted into the substrate via stack i in exposure step i (i=1, . . . , I). t(i) and Pt(i) are computed such that: Vi is maximal through deployment of source t(i) as compared with deployment of any other source for i=1, . . . , I; and an error E being a function of |V1−S1|, |V2−S2|, . . . , |VI−SI| is about minimized with respect to Pi (i=1, . . . , I).