Wafer Pedestal Auto-Calibration for Thermal Offset Alignment

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Solution Overview

Problem

In semiconductor processing systems, accurate placement of wafers within process modules is challenging due to temperature-induced offsets of the pedestal location, which can lead to errors and larger form factors for semiconductor devices and integrated circuits.

Innovation Solution

A method for calibrating the rotation axis of a process module under temperature conditions involves delivering a wafer, detecting entry and exit offsets, and determining the magnitude and direction of temperature-induced offsets using a measurement device outside the module, allowing for correction of the rotation axis alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If coordinates are programmed into the robot during set-up process when the process module is cold, then the set-up process is simple and can be performed by a technician, but the coordinates become inaccurate when the process module is heated or placed under vacuum

Engineering Contradiction:

Improveset-up process simplicityVSAvoidwafer placement accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent performs preliminary calibration actions by delivering a calibration wafer to the pedestal, rotating it to multiple orientations, and measuring its position at each orientation. This preliminary characterization of the pedestal's thermal expansion behavior enables the system to compensate for coordinate shifts that occur when the process module is heated or placed under vacuum, thereby maintaining wafer placement accuracy without complicating the initial set-up process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter being measured from static coordinates to dynamic thermal expansion characteristics. By measuring the calibration wafer's position at multiple rotational orientations and using these measurements to calculate thermal expansion coefficients, the system adapts to temperature-induced coordinate changes, resolving the contradiction between simple set-up and accurate operation under varying thermal conditions

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the process module is heated or placed under vacuum, then the process conditions are achieved for semiconductor processing, but the coordinates of locations within the process module shift

Engineering Contradiction:

Improveprocess temperatureVSAvoidlocation coordinate accuracy

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent implements a feedback mechanism where the measured position of the calibration wafer at multiple rotational orientations is used to calculate the actual thermal expansion of the pedestal. This feedback information is then used to update the coordinate system, allowing the robot to compensate for temperature-induced shifts and maintain accurate wafer placement even when the process module is heated or placed under vacuum

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces the mechanical assumption of fixed coordinates with an optical/measurement-based coordinate determination system. By using a measurement device to detect the calibration wafer's position at multiple orientations and calculating the thermal expansion characteristics, the system substitutes rigid mechanical coordinate references with adaptive, temperature-compensated coordinates, thereby maintaining precision under varying thermal conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 reduces errors in wafer placement and alignment, enabling smaller form factors for semiconductor devices and integrated circuits by accurately correcting for temperature-induced offsets within the process module.

Implementation Method 1

a measurement device outside the process module to measure an entry offset of the wafer when the wafer enters the process module and measure an exit offset of the wafer when the wafer exits the process module

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Data Source

PatentUS11742229B2Auto-calibration to a station of a process module that spins a wafer

Publication Date: 2023.08.29 LAM RES CORP

AI summary

A method for calibration including determining a temperature induced offset in a pedestal of a process module under a temperature condition for a process. The method includes delivering a wafer to the pedestal of the process module by a robot, and detecting an entry offset. The method includes rotating the wafer over the pedestal by an angle. The method includes removing the wafer from the pedestal by the robot and measuring an exit offset. The method includes determining a magnitude and direction of the temperature induced offset using the entry offset and exit offset.