Flash Lamp Annealing Substrate Alignment for Temperature Measurement
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Solution Overview
Problem
Flash lamp annealing in semiconductor wafer processing causes sudden thermal expansion, leading to substrate warping and errors in temperature measurement due to the rapid increase in surface temperature, which complicates accurate emissivity determination and subsequent temperature measurement.
Innovation Solution
A heat treatment apparatus with an alignment mechanism that adjusts the substrate's orientation so that the diameter of minimum warp coincides with the optical axis of the radiation thermometer, or uses multiple thermometers to ensure accurate temperature measurement by minimizing warp along the measurement axis, thereby maintaining consistent emissivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flash lamp annealing is used to rapidly heat the substrate surface, then the impurity activation is achieved without deep diffusion, but the substrate warps due to sudden thermal expansion causing measurement errors
Solution Approach 1:
The patent applies preliminary action by pre-aligning the substrate orientation before flash lamp annealing. The alignment mechanism positions the substrate such that the diagonal direction (where minimal warp occurs) coincides with the optical axis of the radiation thermometer before the heating process begins. This preparatory alignment ensures that even when warping occurs during rapid heating, the measurement accuracy is preserved.
2Ease of operation
If radiation thermometer is used to measure substrate temperature, then non-contact temperature measurement is achieved, but measurement accuracy is reduced due to substrate warping changing emissivity
Solution Approach 1:
The patent applies local quality by focusing the measurement on a specific region of the substrate where emissivity remains stable. By aligning the optical axis with the diagonal direction where minimal warp occurs, the radiation thermometer measures temperature in a localized area that maintains consistent emissivity characteristics, thereby preserving measurement accuracy despite overall substrate warping.
Solution Approach 2:
The patent applies parameter changes by optimizing the geometric relationship between the substrate, flash lamp, and radiation thermometer. Specifically, the substrate is positioned at a 45-degree angle (diagonal orientation) relative to the flash lamp irradiation direction, which minimizes warp along the measurement axis and stabilizes the emissivity parameter for accurate temperature measurement.
3Measurement precision
If substrate orientation is adjusted to align minimum warp direction with optical axis, then temperature measurement accuracy is improved, but device complexity increases due to alignment mechanism
Solution Approach 1:
The patent applies self-service by utilizing the substrate's own geometric properties (its diagonal direction where minimal warp occurs) to achieve accurate measurement. The alignment mechanism simply needs to position the substrate according to its inherent geometric characteristics rather than requiring complex real-time warp compensation systems. The substrate essentially aligns itself with the measurement axis through controlled positioning.
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 allows for precise temperature measurement of the substrate surface during flash lamp annealing, reducing errors associated with substrate warping and ensuring accurate temperature control.
Implementation Method 1
The spectral distribution of light emitted from a xenon flash lamp ranges from an ultraviolet region to a near-infrared region that is a shorter wavelength than the wavelength of light from a conventional halogen lamp, and nearly coincides with a base absorption band of a silicon semiconductor wafer. Therefore, irradiation of the semiconductor wafer with a flash of light from the xenon flash lamp can produce less transmitted light to rapidly increase the temperature of the semiconductor wafer.
Implementation Method 2
a radiation thermometer that is disposed diagonally above the substrate placed on the susceptor and receives infrared radiation emitted from an upper surface of the substrate to measure a temperature of the upper surface
Implementation Method 3
a front surface of a semiconductor wafer is instantaneously irradiated with a flash of light having extremely high energy, so that the temperature of the front surface of the semiconductor wafer rapidly increases in an instant, causing sudden thermal expansion on the front surface of the wafer to deform the semiconductor wafer in a warped form.
Data Source
AI summary
A semiconductor wafer that has a plane orientation of (100) and is made of monocrystalline silicon is warped along an axis, i.e., a diameter along a <100> direction of the semiconductor wafer when irradiated with a flash of light. The semiconductor wafer is placed on a susceptor while the direction of the semiconductor wafer is adjusted so that the diameter along the <100> direction coincides with an optical axis of an upper radiation thermometer. This adjustment makes a diameter along a direction in which a warp of the semiconductor wafer is smallest during irradiation with a flash of light coincide with the optical axis of the upper radiation thermometer. As a result, the semiconductor wafer is hardly warped along the optical axis direction of the upper radiation thermometer even during irradiation with a flash of light, thus hardly changing the emissivity of the semiconductor wafer, so that it is possible to accurately measure the temperature of an upper surface of the semiconductor wafer.