Wafer Temperature Sensing in Ion Implantation Without Contact
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Solution Overview
Problem
Conventional ion implantation systems face inaccuracies in wafer temperature measurement, particularly when using infrared emission detection or contact temperature sensors, which are unreliable at low temperatures and can introduce backside particles or absorb infrared light, leading to undesirable results.
Innovation Solution
The system employs non-contact temperature measurement methods such as single-laser, bandgap, capacitance, and photoluminescence techniques to determine wafer temperature based on diameter, bandgap value, and photoluminescence characteristics, respectively, using laser beams, capacitive sensors, and spectrophotometers, ensuring accurate temperature monitoring without physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared emission detection or contact temperature sensors are used to measure wafer temperature, then temperature measurement can be performed, but measurement accuracy deteriorates at low temperatures and contact sensors may introduce backside particles or absorb infrared light
Solution Approach 1:
The patent replaces contact-based temperature sensors with non-contact optical measurement methods. Specifically, it uses photoluminescence excitation with a 633nm laser to measure wafer temperature through optical properties rather than physical contact, thereby avoiding particle contamination and infrared absorption issues while maintaining measurement accuracy across a wide temperature range including low temperatures
Solution Approach 2:
The patent changes the measurement parameter from infrared emission detection to photoluminescence excitation at 633nm wavelength. This parameter change allows accurate temperature measurement at low temperatures where infrared detection fails, and eliminates the problem of infrared light absorption by measurement devices
2Measurement precision
If contact temperature sensors are used to measure wafer temperature, then temperature can be measured, but backside particles are introduced and wafer integrity is compromised
Solution Approach 1:
The patent replaces mechanical contact sensors with optical measurement using a 633nm laser for photoluminescence excitation. This substitution eliminates physical contact between the sensor and wafer backside, thereby preventing particle contamination while maintaining temperature measurement capability through optical property changes
Solution Approach 2:
The patent introduces light (633nm laser) as an intermediary to transfer measurement information from the wafer without physical contact. The laser excites photoluminescence in the wafer material, and the emitted light carries temperature information, serving as a non-contact mediator that avoids particle generation
3Measurement precision
If infrared light is used for temperature measurement, then temperature detection is enabled, but infrared light absorption by measurement devices occurs leading to measurement errors
Solution Approach 1:
The patent changes the measurement wavelength parameter from infrared to visible light at 633nm. This parameter change avoids the infrared absorption problem entirely, as the measurement device does not absorb the measurement light, eliminating a major source of measurement error while maintaining temperature detection capability
Solution Approach 2:
The patent converts the potential harm of light absorption into a benefit by selecting a wavelength (633nm) where the measurement device does not absorb light. This wavelength choice turns the limitation of infrared absorption into an advantage by using a spectral region with minimal absorption, improving measurement accuracy
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
These methods provide reliable, efficient, and accurate temperature measurements across various ion implantation processes, reducing errors and maintaining wafer integrity by avoiding contact-based measurement issues and infrared interference.
Implementation Method 1
measuring a first distance from a first position of a laser source to a first point on an edge of the wafer by directing a first laser beam from the laser source at the first position to the first point
Implementation Method 2
directing, at a first side of the wafer, a laser beam from a laser source, wherein the laser beam is transmitted through the wafer; generating an absorption profile of the wafer across the predefined frequency range by measuring an intensity of the transmitted laser beam
Implementation Method 3
a processing station is configured to measure a temperature of a wafer using a photoluminescence method. In some examples, this method includes: after heating or cooling the wafer, directing a laser beam from a laser source to a predefined location on the wafer; detecting, using a spectrophotometer or a monochromator, fluorescent light emitted by the wafer
Data Source
AI summary
The present disclosure relates generally to ion implantation, and more particularly, to systems and processes for measuring the temperature of a wafer within an ion implantation system. An exemplary ion implantation system may include a robotic arm, one or more load lock chambers, a pre-implantation station, an ion implanter, a post-implantation station, and a controller. The pre-implantation station is configured to heat or cool a wafer prior to the wafer being implanted with ions by the ion implanter. The post-implantation station is configured to heat or cool a wafer after the wafer is implanted with ions by the ion implanter. The pre-implantation station and/or post-implantation station are further configured to measure a current temperature of a wafer. The controller is configured to control the various components and processes described above, and to determine a current temperature of a wafer based on information received from the pre-implantation station and/or post-implantation station.