Flash Lamp Energy Control via Reflected Light Ratio
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Solution Overview
Problem
Conventional heat treatment processes for semiconductor wafers using xenon flash lamps face challenges in optimizing light energy exposure due to variations in light absorption characteristics between patterned and unpatterned wafers, leading to potential wafer cracks and inefficiencies, and require frequent calibration that disrupts the operation of heat treatment apparatuses.
Innovation Solution
A reflected light intensity ratio measuring device and a heat treatment apparatus that utilize a calibration standard member to calculate the light energy absorption ratio of patterned wafers relative to unpatterned wafers, allowing for real-time adjustments in light energy exposure without stopping the apparatus, using a calibration standard member that mimics the surface properties of a standard substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If xenon flash lamp is used to rapidly raise the temperature of the wafer surface, then ion activation is achieved without deep ion diffusion, but wafer cracks or slips may occur due to excessive energy causing abrupt surface expansion
Solution Approach 1:
The system measures the reflected light intensity ratio of the wafer to a standard substrate, uses this measurement to calculate the light energy absorption ratio, and adjusts the flash lamp energy accordingly. This closed-loop feedback control optimizes the energy input to achieve ion activation while preventing wafer damage from excessive energy.
Solution Approach 2:
The system dynamically adjusts the light energy parameter of the flash lamp based on the measured reflected light intensity ratio. By changing the energy parameter according to actual wafer absorption characteristics, the system achieves precise control over the heating process, preventing both under-heating and overheating that could cause cracks.
2Manufacturing precision
If light energy is optimized for unpatterned wafers, then ion activation is achieved, but patterned wafers absorb more light energy resulting in wafer cracks
Solution Approach 1:
The system measures the reflected light intensity ratio for each wafer (patterned or unpatterned) and adjusts the flash lamp energy based on this measurement. This feedback mechanism allows the system to adapt to different wafer types and their varying light absorption characteristics, preventing cracks in patterned wafers while ensuring proper ion activation.
Solution Approach 2:
The system recognizes that different wafer regions (patterned vs. unpatterned) have different light absorption properties and adjusts the energy input accordingly. By treating each wafer's light absorption characteristics as a local property that requires individual optimization, the system prevents damage to patterned regions.
3Measurement precision
If frequent calibration is performed to account for variations in light absorption characteristics, then measurement precision is improved, but apparatus operation is disrupted
Solution Approach 1:
The system performs calibration measurements continuously during normal operation by utilizing the reflected light intensity measurement capability. The calibration standard member is measured in sequence with wafers, allowing the system to maintain measurement precision without interrupting the production flow, as the calibration is integrated into the continuous processing sequence.
4Manufacturing precision
If reflected light intensity ratio measurement is implemented to calculate light energy absorption ratio, then light energy optimization is achieved, but device complexity increases
Solution Approach 1:
The system introduces a calibration standard member as an intermediary reference object with known reflective properties. By comparing the wafer's reflected light intensity to this standard, the system can calculate the light energy absorption ratio without requiring complex absolute measurements, thereby optimizing light energy exposure while limiting the increase in device complexity.
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
Enables continuous operation of the heat treatment apparatus by allowing for on-the-fly calibration and precise adjustment of light energy exposure, preventing wafer damage and improving processing efficiency by accounting for individual wafer absorption characteristics.
Implementation Method 1
a light emitting and receiving part fixed to the chamber for directing light onto a main surface of the object substrate held by the substrate holding part and for receiving light reflected from the main surface
Implementation Method 2
The xenon flash lamp has a spectral distribution of radiation ranging from ultraviolet to near-infrared regions. The wavelength of light emitted from the xenon flash lamp is shorter than that of light emitted from the conventional halogen lamp, and approximately coincides with a basic absorption band of a silicon semiconductor wafer. It is therefore possible to rapidly raise the temperature of the semiconductor wafer
Implementation Method 3
a calibration standard member placed in an optical path of light emerging from the light emitting and receiving part, the calibration standard member being similar in surface property to the standard substrate
Data Source
AI summary
A measuring optical system for emitting and receiving light is fixedly installed in a ceiling portion of a measuring device, and a wafer holding part for supporting a semiconductor wafer is provided in a bottom portion of the measuring device. A support table is horizontally laid between support pins of the wafer holding part, and a calibration standard member for calibration is placed on an upper surface of the support table. When a semiconductor wafer is supported by the support pins, light emerging from the measuring optical system impinges upon the semiconductor wafer, and the reflection intensity of the light is measured. When no semiconductor wafer is supported by the support pins, light emerging from the measuring optical system impinges upon the calibration standard member, whereby the calibration can be done at any time.